zstd: don't call zstd_mempool_reap if there are no buffers #16302
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cc @behlendorf |
allanjude
approved these changes
Jun 27, 2024
tonyhutter
approved these changes
Jul 12, 2024
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Just noticed a minor checkstyle error: Would you mind updating your commit message? |
zfs_zstd_cache_reap_now is issued every second.
zstd_mempool_reap checks for both pool existence and buffer count, but
that's still 2 func calls which are trivially avoidable.
With clang it even avoids pushing the stack pointer (but still suffers
the mispredict due to a forward jump, not modified in case someone is
using zstd):
<+0>: cmpq $0x0,0x0(%rip) # <zfs_zstd_cache_reap_now+8>
<+8>: je 0x217de4 <zfs_zstd_cache_reap_now+36>
<+10>: push %rbp
<+11>: mov %rsp,%rbp
<+14>: mov 0x0(%rip),%rdi # <zfs_zstd_cache_reap_now+21>
<+21>: call 0x217df0 <zstd_mempool_reap>
<+26>: mov 0x0(%rip),%rdi # <zfs_zstd_cache_reap_now+33>
<+33>: pop %rbp
<+34>: jmp 0x217df0 <zstd_mempool_reap>
<+36>: ret
Preferably the call would not be made to begin with if zstd is not used,
but this retains all the logic confined to zstd code.
Sponsored by: Rubicon Communications, LLC ("Netgate")
Signed-off-by: Mateusz Guzik <[email protected]>
calccrypto
pushed a commit
to hpc/zfs
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this pull request
Jul 17, 2024
…6302) zfs_zstd_cache_reap_now is issued every second. zstd_mempool_reap checks for both pool existence and buffer count, but that's still 2 func calls which are trivially avoidable. With clang it even avoids pushing the stack pointer (but still suffers the mispredict due to a forward jump, not modified in case someone is using zstd): <+0>: cmpq $0x0,0x0(%rip) # <zfs_zstd_cache_reap_now+8> <+8>: je 0x217de4 <zfs_zstd_cache_reap_now+36> <+10>: push %rbp <+11>: mov %rsp,%rbp <+14>: mov 0x0(%rip),%rdi # <zfs_zstd_cache_reap_now+21> <+21>: call 0x217df0 <zstd_mempool_reap> <+26>: mov 0x0(%rip),%rdi # <zfs_zstd_cache_reap_now+33> <+33>: pop %rbp <+34>: jmp 0x217df0 <zstd_mempool_reap> <+36>: ret Preferably the call would not be made to begin with if zstd is not used, but this retains all the logic confined to zstd code. Sponsored by: Rubicon Communications, LLC ("Netgate") Signed-off-by: Mateusz Guzik <[email protected]> Reviewed-by: Allan Jude <[email protected]> Reviewed-by: Tony Hutter <[email protected]>
lundman
pushed a commit
to openzfsonwindows/openzfs
that referenced
this pull request
Sep 4, 2024
…6302) zfs_zstd_cache_reap_now is issued every second. zstd_mempool_reap checks for both pool existence and buffer count, but that's still 2 func calls which are trivially avoidable. With clang it even avoids pushing the stack pointer (but still suffers the mispredict due to a forward jump, not modified in case someone is using zstd): <+0>: cmpq $0x0,0x0(%rip) # <zfs_zstd_cache_reap_now+8> <+8>: je 0x217de4 <zfs_zstd_cache_reap_now+36> <+10>: push %rbp <+11>: mov %rsp,%rbp <+14>: mov 0x0(%rip),%rdi # <zfs_zstd_cache_reap_now+21> <+21>: call 0x217df0 <zstd_mempool_reap> <+26>: mov 0x0(%rip),%rdi # <zfs_zstd_cache_reap_now+33> <+33>: pop %rbp <+34>: jmp 0x217df0 <zstd_mempool_reap> <+36>: ret Preferably the call would not be made to begin with if zstd is not used, but this retains all the logic confined to zstd code. Sponsored by: Rubicon Communications, LLC ("Netgate") Signed-off-by: Mateusz Guzik <[email protected]> Reviewed-by: Allan Jude <[email protected]> Reviewed-by: Tony Hutter <[email protected]>
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zfs_zstd_cache_reap_now is issued every second.
zstd_mempool_reap checks for both pool existence and buffer count, but that's still 2 func calls which are trivially avoidable.
With clang it even avoids pushing the stack pointer:
Preferably the call would not be made to begin with if zstd is not used, but this retains all the logic confined to zstd code.
Sponsored by: Rubicon Communications, LLC ("Netgate")
Signed-off-by: Mateusz Guzik [email protected]
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