tree 230ed30102aa5c8a8eb3aebfc8f62b8c5c2e4516
parent a85d391fbba047667b0be41effbce41de4b28c29
author Federico 'Morg' Pareschi <morg@google.com> 1670552454 +0000
committer crosvm LUCI <crosvm-scoped@luci-project-accounts.iam.gserviceaccount.com> 1671518538 +0000

Reland "fs: Reduce number of open() calls in passthroughfs"

This is a reland of commit 55a9bccead02fe03839f6a31dcd3b4a070f1c481

The fix is to make sure we drop to the lock guard acquired by the
inodes mutex, so we don't end up in a deadlock. By splitting the if
statement and separating the else block, the guard is dropped
automatically.

Original change's description:
> fs: Reduce number of open() calls in passthroughfs
>
> Instead of always opening a new file every time we do an entry lookup,
> check first if the entry already exists in our inode map.
>
> I ran a trace test while loading a game on arcvm with and without this
> patch.
>
> Without patch:
> System-wide trace:
> newfstatat calls = 19211
> openat calls = 13189
> ~68% ratio of all newstat() calls vs openat() call
>
> virtiofs trace:
> newfstatat calls = 11958
> openat calls = 9899
> 82% ratio of virtiofs newstat() calls vs openat() call
>
> With patch:
> System-wide trace:
> newfstatat calls = 20242
> openat calls = 12954
> 64% ratio of all newstat() calls vs openat() call
>
> virtiofs trace:
> newfstatat calls = 2223
> openat = 273
> ~12% ratio of virtiofs newstat() calls vs openat() call
>
> This is a significant reduction of unnecessary syscalls in virtiofs
> (82% -> 12%)
>
> BUG=b:261922849
> TEST=loaded a game in arcvm and compared syscall % count
>
> Change-Id: I28acbae05900d9735ba3730ee106368ddc792476
> Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4091563
> Auto-Submit: Morg <morg@chromium.org>
> Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
> Commit-Queue: Keiichi Watanabe <keiichiw@chromium.org>

Bug: b:261922849
Change-Id: Ib885cb5f2b3f725405df2eecc641228042ea2093
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/4105201
Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
Commit-Queue: Keiichi Watanabe <keiichiw@chromium.org>
Auto-Submit: Morg <morg@chromium.org>