ZFS secondarycache on SSD problem on r255173

[Steven Hartland]

Hows things looking Vitalij?

----- Original Message ----- 
From: "Vitalij Satanivskij" <satan at ukr.net>


> Ok. Just right now system rebooted with you patch.
> 
> Trim enabled again.
> 
> WIll wait some time untile size of used cache grow's.
> 
> 
> Steven Hartland wrote:
> SH> Looking at the l2arc compression code I believe that metadata is always
> SH> compressed with lz4, even if compression is off on all datasets.
> SH> 
> SH> This is backed up by what I'm seeing on my system here as it shows a
> SH> non-zero l2_compress_successes value even though I'm not using
> SH> compression at all.
> SH> 
> SH> I think we we may well need the following patch to set the minblock
> SH> size based on the vdev ashift and not SPA_MINBLOCKSIZE.
> SH> 
> SH> svn diff -x -p sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
> SH> Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c
> SH> ===================================================================
> SH> --- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c        (revision 256554)
> SH> +++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c        (working copy)
> SH> @@ -5147,7 +5147,7 @@ l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr)
> SH>         len = l2hdr->b_asize;
> SH>         cdata = zio_data_buf_alloc(len);
> SH>         csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata,
> SH> -           cdata, l2hdr->b_asize, (size_t)SPA_MINBLOCKSIZE);
> SH> +           cdata, l2hdr->b_asize, (size_t)(1ULL << l2hdr->b_dev->l2ad_vdev->vdev_ashift));
> SH> 
> SH>         if (csize == 0) {
> SH>                 /* zero block, indicate that there's nothing to write */
> SH> 
> SH> Could you try this patch on your system Vitalij see if it has any effect
> SH> on the number of l2_cksum_bad / l2_io_error?


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