Tags: chiyutianyi/git
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negotiator/skipping: fix some problems in mark_common() The mark_common() method in negotiator/skipping.c was converted from recursive to iterative in 4654134 (negotiator/skipping: avoid stack overflow, 2022-10-25), but there is some more work to do: 1. prio_queue() should be used with clear_prio_queue(), otherwise there will be a memory leak. 2. It does not do duplicate protection before prio_queue_put(). (The COMMON bit would work here, too.) 3. When it translated from recursive to iterative it kept "return" statements that should probably be "continue" statements. 4. It does not attempt to parse commits, and instead returns immediately when finding an unparsed commit. This is something that it did in its original version, so maybe it is by design, but it doesn't match the doc comment for the method. Helped-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Han Xin <hanxin.hx@bytedance.com>
negotiator/default.c: avoid stack overflow mark_common() in negotiator/default.c may overflow the stack due to recursive function calls. Avoid this by instead recursing using a heap-allocated data structure. This is the same case as [1]. 1. https://lore.kernel.org/git/20221025232934.1504445-1-jonathantanmy@google.com/ Reported-by: Xin Xing <xingxin.xx@bytedance.com> Signed-off-by: Han Xin <hanxin.hx@bytedance.com>
commit-graph.c: no lazy fetch in lookup_commit_in_graph() The commit-graph is used to opportunistically optimize accesses to certain pieces of information on commit objects, and lookup_commit_in_graph() tries to say "no" when the requested commit does not locally exist by returning NULL, in which case the caller can ask for (which may result in on-demand fetching from a promisor remote) and parse the commit object itself. However, it uses a wrong helper, repo_has_object_file(), to do so. This helper not only checks if an object is mmediately available in the local object store, but also tries to fetch from a promisor remote. But the fetch machinery calls lookup_commit_in_graph(), thus causing an infinite loop. We should make lookup_commit_in_graph() expect that a commit given to it can be legitimately missing from the local object store, by using the has_object_file() helper instead. Signed-off-by: Han Xin <hanxin.hx@bytedance.com>
commit-graph.c: no lazy fetch in lookup_commit_in_graph() The commit-graph is used to opportunistically optimize accesses to certain pieces of information on commit objects, and lookup_commit_in_graph() tries to say "no" when the requested commit does not locally exist by returning NULL, in which case the caller can ask for (which may result in on-demand fetching from a promisor remote) and parse the commit object itself. However, it uses a wrong helper, repo_has_object_file(), to do so. This helper not only checks if an object is mmediately available in the local object store, but also tries to fetch from a promisor remote. But the fetch machinery calls lookup_commit_in_graph(), thus causing an infinite loop. We should make lookup_commit_in_graph() expect that a commit given to it can be legitimately missing from the local object store, by using the has_object_file() helper instead. Signed-off-by: Han Xin <hanxin.hx@bytedance.com>
commit-graph.c: no lazy fetch in lookup_commit_in_graph() If a commit is in the commit graph, we would expect the commit to also be present. So we should use has_object() instead of repo_has_object_file(), which will help us avoid getting into an endless loop of lazy fetch. When we found the commit in the graph in lookup_commit_in_graph(), but the commit is missing from the repository, we will try promisor_remote_get_direct() and then enter another loop. While sometimes it will finally succeed because it cannot fork subprocess, it has exhausted the local process resources and can be harmful to the remote service. Signed-off-by: Han Xin <hanxin.hx@bytedance.com>
commit-graph.c: no lazy fetch in lookup_commit_in_graph() If a commit is in the commit graph, we would expect the commit to also be present. So we should use has_object() instead of repo_has_object_file(), which may start a new lazy fetch. We can see the endless loop issue via this[1]. 1. https://lore.kernel.org/git/20220612161707.21807-1-chiyutianyi@gmail.com/ Signed-off-by: Han Xin <hanxin.hx@bytedance.com>
unpack-objects: use stream_loose_object() to unpack large objects Make use of the stream_loose_object() function introduced in the preceding commit to unpack large objects. Before this we'd need to malloc() the size of the blob before unpacking it, which could cause OOM with very large blobs. We could use the new streaming interface to unpack all blobs, but doing so would be much slower, as demonstrated e.g. with this benchmark using git-hyperfine[0]: rm -rf /tmp/scalar.git && git clone --bare https://github.com/Microsoft/scalar.git /tmp/scalar.git && mv /tmp/scalar.git/objects/pack/*.pack /tmp/scalar.git/my.pack && git hyperfine \ -r 2 --warmup 1 \ -L rev origin/master,HEAD -L v "10,512,1k,1m" \ -s 'make' \ -p 'git init --bare dest.git' \ -c 'rm -rf dest.git' \ './git -C dest.git -c core.bigFileThreshold={v} unpack-objects </tmp/scalar.git/my.pack' Here we'll perform worse with lower core.bigFileThreshold settings with this change in terms of speed, but we're getting lower memory use in return: Summary './git -C dest.git -c core.bigFileThreshold=10 unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' ran 1.01 ± 0.01 times faster than './git -C dest.git -c core.bigFileThreshold=1k unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' 1.01 ± 0.01 times faster than './git -C dest.git -c core.bigFileThreshold=1m unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' 1.01 ± 0.02 times faster than './git -C dest.git -c core.bigFileThreshold=1m unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' 1.02 ± 0.00 times faster than './git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' 1.09 ± 0.01 times faster than './git -C dest.git -c core.bigFileThreshold=1k unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' 1.10 ± 0.00 times faster than './git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' 1.11 ± 0.00 times faster than './git -C dest.git -c core.bigFileThreshold=10 unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' A better benchmark to demonstrate the benefits of that this one, which creates an artificial repo with a 1, 25, 50, 75 and 100MB blob: rm -rf /tmp/repo && git init /tmp/repo && ( cd /tmp/repo && for i in 1 25 50 75 100 do dd if=/dev/urandom of=blob.$i count=$(($i*1024)) bs=1024 done && git add blob.* && git commit -mblobs && git gc && PACK=$(echo .git/objects/pack/pack-*.pack) && cp "$PACK" my.pack ) && git hyperfine \ --show-output \ -L rev origin/master,HEAD -L v "512,50m,100m" \ -s 'make' \ -p 'git init --bare dest.git' \ -c 'rm -rf dest.git' \ '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold={v} unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' Using this test we'll always use >100MB of memory on origin/master (around ~105MB), but max out at e.g. ~55MB if we set core.bigFileThreshold=50m. The relevant "Maximum resident set size" lines were manually added below the relevant benchmark: '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=50m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'origin/master' ran Maximum resident set size (kbytes): 107080 1.02 ± 0.78 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'origin/master' Maximum resident set size (kbytes): 106968 1.09 ± 0.79 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=100m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'origin/master' Maximum resident set size (kbytes): 107032 1.42 ± 1.07 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=100m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'HEAD' Maximum resident set size (kbytes): 107072 1.83 ± 1.02 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=50m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'HEAD' Maximum resident set size (kbytes): 55704 2.16 ± 1.19 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'HEAD' Maximum resident set size (kbytes): 4564 This shows that if you have enough memory this new streaming method is slower the lower you set the streaming threshold, but the benefit is more bounded memory use. An earlier version of this patch introduced a new "core.bigFileStreamingThreshold" instead of re-using the existing "core.bigFileThreshold" variable[1]. As noted in a detailed overview of its users in [2] using it has several different meanings. Still, we consider it good enough to simply re-use it. While it's possible that someone might want to e.g. consider objects "small" for the purposes of diffing but "big" for the purposes of writing them such use-cases are probably too obscure to worry about. We can always split up "core.bigFileThreshold" in the future if there's a need for that. 0. https://github.com/avar/git-hyperfine/ 1. https://lore.kernel.org/git/20211210103435.83656-1-chiyutianyi@gmail.com/ 2. https://lore.kernel.org/git/20220120112114.47618-5-chiyutianyi@gmail.com/ Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Helped-by: Derrick Stolee <stolee@gmail.com> Helped-by: Jiang Xin <zhiyou.jx@alibaba-inc.com> Signed-off-by: Han Xin <chiyutianyi@gmail.com> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
unpack-objects: use stream_loose_object() to unpack large objects Make use of the stream_loose_object() function introduced in the preceding commit to unpack large objects. Before this we'd need to malloc() the size of the blob before unpacking it, which could cause OOM with very large blobs. We could use the new streaming interface to unpack all blobs, but doing so would be much slower, as demonstrated e.g. with this benchmark using git-hyperfine[0]: rm -rf /tmp/scalar.git && git clone --bare https://github.com/Microsoft/scalar.git /tmp/scalar.git && mv /tmp/scalar.git/objects/pack/*.pack /tmp/scalar.git/my.pack && git hyperfine \ -r 2 --warmup 1 \ -L rev origin/master,HEAD -L v "10,512,1k,1m" \ -s 'make' \ -p 'git init --bare dest.git' \ -c 'rm -rf dest.git' \ './git -C dest.git -c core.bigFileThreshold={v} unpack-objects </tmp/scalar.git/my.pack' Here we'll perform worse with lower core.bigFileThreshold settings with this change in terms of speed, but we're getting lower memory use in return: Summary './git -C dest.git -c core.bigFileThreshold=10 unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' ran 1.01 ± 0.01 times faster than './git -C dest.git -c core.bigFileThreshold=1k unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' 1.01 ± 0.01 times faster than './git -C dest.git -c core.bigFileThreshold=1m unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' 1.01 ± 0.02 times faster than './git -C dest.git -c core.bigFileThreshold=1m unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' 1.02 ± 0.00 times faster than './git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' 1.09 ± 0.01 times faster than './git -C dest.git -c core.bigFileThreshold=1k unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' 1.10 ± 0.00 times faster than './git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' 1.11 ± 0.00 times faster than './git -C dest.git -c core.bigFileThreshold=10 unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' A better benchmark to demonstrate the benefits of that this one, which creates an artificial repo with a 1, 25, 50, 75 and 100MB blob: rm -rf /tmp/repo && git init /tmp/repo && ( cd /tmp/repo && for i in 1 25 50 75 100 do dd if=/dev/urandom of=blob.$i count=$(($i*1024)) bs=1024 done && git add blob.* && git commit -mblobs && git gc && PACK=$(echo .git/objects/pack/pack-*.pack) && cp "$PACK" my.pack ) && git hyperfine \ --show-output \ -L rev origin/master,HEAD -L v "512,50m,100m" \ -s 'make' \ -p 'git init --bare dest.git' \ -c 'rm -rf dest.git' \ '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold={v} unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' Using this test we'll always use >100MB of memory on origin/master (around ~105MB), but max out at e.g. ~55MB if we set core.bigFileThreshold=50m. The relevant "Maximum resident set size" lines were manually added below the relevant benchmark: '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=50m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'origin/master' ran Maximum resident set size (kbytes): 107080 1.02 ± 0.78 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'origin/master' Maximum resident set size (kbytes): 106968 1.09 ± 0.79 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=100m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'origin/master' Maximum resident set size (kbytes): 107032 1.42 ± 1.07 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=100m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'HEAD' Maximum resident set size (kbytes): 107072 1.83 ± 1.02 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=50m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'HEAD' Maximum resident set size (kbytes): 55704 2.16 ± 1.19 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'HEAD' Maximum resident set size (kbytes): 4564 This shows that if you have enough memory this new streaming method is slower the lower you set the streaming threshold, but the benefit is more bounded memory use. An earlier version of this patch introduced a new "core.bigFileStreamingThreshold" instead of re-using the existing "core.bigFileThreshold" variable[1]. As noted in a detailed overview of its users in [2] using it has several different meanings. Still, we consider it good enough to simply re-use it. While it's possible that someone might want to e.g. consider objects "small" for the purposes of diffing but "big" for the purposes of writing them such use-cases are probably too obscure to worry about. We can always split up "core.bigFileThreshold" in the future if there's a need for that. 0. https://github.com/avar/git-hyperfine/ 1. https://lore.kernel.org/git/20211210103435.83656-1-chiyutianyi@gmail.com/ 2. https://lore.kernel.org/git/20220120112114.47618-5-chiyutianyi@gmail.com/ Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Helped-by: Derrick Stolee <stolee@gmail.com> Helped-by: Jiang Xin <zhiyou.jx@alibaba-inc.com> Signed-off-by: Han Xin <hanxin.hx@alibaba-inc.com> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
unpack-objects: use stream_loose_object() to unpack large objects Make use of the stream_loose_object() function introduced in the preceding commit to unpack large objects. Before this we'd need to malloc() the size of the blob before unpacking it, which could cause OOM with very large blobs. We could use the new streaming interface to unpack all blobs, but doing so would be much slower, as demonstrated e.g. with this benchmark using git-hyperfine[0]: rm -rf /tmp/scalar.git && git clone --bare https://github.com/Microsoft/scalar.git /tmp/scalar.git && mv /tmp/scalar.git/objects/pack/*.pack /tmp/scalar.git/my.pack && git hyperfine \ -r 2 --warmup 1 \ -L rev origin/master,HEAD -L v "10,512,1k,1m" \ -s 'make' \ -p 'git init --bare dest.git' \ -c 'rm -rf dest.git' \ './git -C dest.git -c core.bigFileThreshold={v} unpack-objects </tmp/scalar.git/my.pack' Here we'll perform worse with lower core.bigFileThreshold settings with this change in terms of speed, but we're getting lower memory use in return: Summary './git -C dest.git -c core.bigFileThreshold=10 unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' ran 1.01 ± 0.01 times faster than './git -C dest.git -c core.bigFileThreshold=1k unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' 1.01 ± 0.01 times faster than './git -C dest.git -c core.bigFileThreshold=1m unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' 1.01 ± 0.02 times faster than './git -C dest.git -c core.bigFileThreshold=1m unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' 1.02 ± 0.00 times faster than './git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/scalar.git/my.pack' in 'origin/master' 1.09 ± 0.01 times faster than './git -C dest.git -c core.bigFileThreshold=1k unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' 1.10 ± 0.00 times faster than './git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' 1.11 ± 0.00 times faster than './git -C dest.git -c core.bigFileThreshold=10 unpack-objects </tmp/scalar.git/my.pack' in 'HEAD' A better benchmark to demonstrate the benefits of that this one, which creates an artificial repo with a 1, 25, 50, 75 and 100MB blob: rm -rf /tmp/repo && git init /tmp/repo && ( cd /tmp/repo && for i in 1 25 50 75 100 do dd if=/dev/urandom of=blob.$i count=$(($i*1024)) bs=1024 done && git add blob.* && git commit -mblobs && git gc && PACK=$(echo .git/objects/pack/pack-*.pack) && cp "$PACK" my.pack ) && git hyperfine \ --show-output \ -L rev origin/master,HEAD -L v "512,50m,100m" \ -s 'make' \ -p 'git init --bare dest.git' \ -c 'rm -rf dest.git' \ '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold={v} unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' Using this test we'll always use >100MB of memory on origin/master (around ~105MB), but max out at e.g. ~55MB if we set core.bigFileThreshold=50m. The relevant "Maximum resident set size" lines were manually added below the relevant benchmark: '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=50m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'origin/master' ran Maximum resident set size (kbytes): 107080 1.02 ± 0.78 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'origin/master' Maximum resident set size (kbytes): 106968 1.09 ± 0.79 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=100m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'origin/master' Maximum resident set size (kbytes): 107032 1.42 ± 1.07 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=100m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'HEAD' Maximum resident set size (kbytes): 107072 1.83 ± 1.02 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=50m unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'HEAD' Maximum resident set size (kbytes): 55704 2.16 ± 1.19 times faster than '/usr/bin/time -v ./git -C dest.git -c core.bigFileThreshold=512 unpack-objects </tmp/repo/my.pack 2>&1 | grep Maximum' in 'HEAD' Maximum resident set size (kbytes): 4564 This shows that if you have enough memory this new streaming method is slower the lower you set the streaming threshold, but the benefit is more bounded memory use. An earlier version of this patch introduced a new "core.bigFileStreamingThreshold" instead of re-using the existing "core.bigFileThreshold" variable[1]. As noted in a detailed overview of its users in [2] using it has several different meanings. Still, we consider it good enough to simply re-use it. While it's possible that someone might want to e.g. consider objects "small" for the purposes of diffing but "big" for the purposes of writing them such use-cases are probably too obscure to worry about. We can always split up "core.bigFileThreshold" in the future if there's a need for that. 0. https://github.com/avar/git-hyperfine/ 1. https://lore.kernel.org/git/20211210103435.83656-1-chiyutianyi@gmail.com/ 2. https://lore.kernel.org/git/20220120112114.47618-5-chiyutianyi@gmail.com/ Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Helped-by: Derrick Stolee <stolee@gmail.com> Helped-by: Jiang Xin <zhiyou.jx@alibaba-inc.com> Signed-off-by: Han Xin <hanxin.hx@alibaba-inc.com> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
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