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SubjectRe: [PATCH, RFC] xfs: batched discard support
Mark Lord wrote:
..
> Slow, but presumably thorough.
> Subsequent runs were equally slow.
>
> The problem is, it still issues TRIMs to the LLD one extent at a time.
> Compare this with doing it all in a single TRIM command
> with the wiper.sh script (filesystem unmounted):
>
> [~] time wiper.sh /dev/sdb3 --commit
>
> wiper.sh: Linux SATA SSD TRIM utility, version 1.9b, by Mark Lord.
> Preparing for offline TRIM of free space on /dev/sdb3 (xfs
> non-mounted).
> This operation could destroy your data. Are you sure (y/N)? y
> Syncing disks..
> Beginning TRIM operations..
> Trimming 168 free extents encompassing 8793136 sectors (4294 MB)
> Done.
>
> real 0m1.249s
> user 0m0.110s
> sys 0m0.063s
>
> That includes the time for me to type 'y' and hit enter. :)
..

For completeness, here's the same operation again,
except this time on the *mounted* xfs filesystem.
It won't be trimming quite as many blocks
(leaves 1% free space in reserve),
but otherwise is similar:

[~] time wiper.sh /dev/sdb3 --commit

wiper.sh: Linux SATA SSD TRIM utility, version 1.9b, by Mark Lord.
Preparing for online TRIM of free space on /dev/sdb3 (xfs mounted read-write at /x).
This operation could destroy your data. Are you sure (y/N)? y
Creating temporary file (4348405 KB)..
Syncing disks..
Beginning TRIM operations..
Trimming 134 free extents encompassing 8696816 sectors (4246 MB)
Removing temporary file..
Syncing disks..
Done.

real 0m1.212s
user 0m0.043s
sys 0m0.053s



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