Re: [Patch] Delete sysfs_dirent.s_count, saving ~100kB on my system

[Adam J. Richter]

Chris Wright wrote:
>* Andrew Morton (akpm@xxxxxxxx) wrote:
>> That's all well and good, but sysfs_new_dirent() should be using a
>> standalone slab cache for allocating sysfs_dirent instances.  That way, we
>> use 36 bytes for each one rather than 64.

>Reasonable, here's a patch (lightly tested).  [...]

	Great.  That way 32-bit architectures should be able to
benefit from some another shrink of sysfs_dirent that I'd like
to do, and it will also help 64-bit architectures (where sysfs_dirent
is still larger than 32 bytes even with my change).

	I applied Chris's patch on top of my own (which still
saves about 14kB on my machine and shrinks the source code by 11
lines) and I am running it now.  It looks fine to me, although I
haven't looked into making a separate slab cache before.  I guess
it's okay that there is no alignment requirement on it for now,
as there are a lot of sysfs_dirent structure and more every day,
and programs that would access these structures frequently would
also probably cause access to a lot of them at the same time (by
scanning the sysfs tree), so inter-processor cache line contention
might be offset by the more efficient utilization of the processor's
cache.

	Chris's patch file applied without conflict (there was a
one line offset in fs/sysfs/sysfs.h), so it should be easy to
integrate both patches.  Please let me know if there is anything
further I should or can do to help make that happen, as I'd like
to have my fs/sysfs tree in sync before trying to unpin the
struct dirent and struct inode for sysfs directories, as I
expect that to be a more complex patch (and unpin hundreds of kbytes).

                    __     ______________
Adam J. Richter        \ /
adam@xxxxxxxxxxxxx      | g g d r a s i l
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