svn commit: r364044 - in head: share/man/man9 sys/compat/linuxkpi/common/src sys/kern sys/security/audit sys/sys

[Mateusz Guzik]

tmpfs_getattr fills > 100 bytes worth of data into struct vattr, which
then has to be converted to struct stat format. The conversion happens
to copy some of it as it is and branch on other stuff. tmpfs_stat
elides the entire process.

On 8/8/20, Alan Somers <asomers at freebsd.org> wrote:
> On Fri, Aug 7, 2020 at 5:06 PM Mateusz Guzik <mjg at freebsd.org> wrote:
>
>> Author: mjg
>> Date: Fri Aug  7 23:06:40 2020
>> New Revision: 364044
>> URL: https://svnweb.freebsd.org/changeset/base/364044
>>
>> Log:
>>   vfs: add VOP_STAT
>>
>>   The current scheme of calling VOP_GETATTR adds avoidable overhead.
>>
>>   An example with tmpfs doing fstat (ops/s):
>>   before: 7488958
>>   after:  7913833
>>
>>   Reviewed by:  kib (previous version)
>>   Differential Revision:        https://reviews.freebsd.org/D25910
>>
>> Modified:
>>   head/share/man/man9/Makefile
>>   head/share/man/man9/VOP_ATTRIB.9
>>   head/sys/compat/linuxkpi/common/src/linux_compat.c
>>   head/sys/kern/vfs_default.c
>>   head/sys/kern/vfs_syscalls.c
>>   head/sys/kern/vfs_vnops.c
>>   head/sys/kern/vnode_if.src
>>   head/sys/security/audit/audit_arg.c
>>   head/sys/sys/vnode.h
>>
>
> What avoidable overhead? The tmpfs_stat handler that you added in your next
> commit looks pretty much the same as vop_getattr.  I'm missing where the
> performance improvement comes from.  Could you please fill me in?
> -Alan
>


-- 
Mateusz Guzik <mjguzik gmail.com>