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[superseded by #3451][RFC, l2arc accounting & checksum issue] l2arc-write-target-size.diff , cumulative patch #3433

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[superseded by #3451][RFC, l2arc accounting & checksum issue] l2arc-write-target-size.diff , cumulative patch #3433

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44 changes: 27 additions & 17 deletions module/zfs/arc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4965,8 +4965,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
{
arc_buf_hdr_t *ab, *ab_prev, *head;
list_t *list;
uint64_t write_asize, write_psize, write_sz, headroom,
buf_compress_minsz;
uint64_t write_asize, write_sz, headroom, buf_compress_minsz;
void *buf_data;
kmutex_t *list_lock = NULL;
boolean_t full;
Expand All @@ -4982,7 +4981,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
*headroom_boost = B_FALSE;

pio = NULL;
write_sz = write_asize = write_psize = 0;
write_sz = write_asize = 0;
full = B_FALSE;
head = kmem_cache_alloc(hdr_cache, KM_PUSHPAGE);
head->b_flags |= ARC_L2_WRITE_HEAD;
Expand Down Expand Up @@ -5021,6 +5020,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
l2arc_buf_hdr_t *l2hdr;
kmutex_t *hash_lock;
uint64_t buf_sz;
uint64_t buf_a_sz;

if (arc_warm == B_FALSE)
ab_prev = list_next(list, ab);
Expand Down Expand Up @@ -5049,7 +5049,15 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
continue;
}

if ((write_sz + ab->b_size) > target_sz) {
/*
* Assume that the buffer is not going to be compressed
* and could take more space on disk because of a larger
* disk block size.
*/
buf_sz = ab->b_size;
buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);

if ((write_asize + buf_a_sz) > target_sz) {
full = B_TRUE;
mutex_exit(hash_lock);
break;
Expand Down Expand Up @@ -5094,7 +5102,6 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
l2hdr->b_tmp_cdata = ab->b_buf->b_data;
l2hdr->b_hits = 0;

buf_sz = ab->b_size;
ab->b_l2hdr = l2hdr;

list_insert_head(dev->l2ad_buflist, ab);
Expand All @@ -5109,6 +5116,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
mutex_exit(hash_lock);

write_sz += buf_sz;
write_asize += buf_a_sz;
}

mutex_exit(list_lock);
Expand All @@ -5130,6 +5138,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
* and work backwards, retracing the course of the buffer selector
* loop above.
*/
write_asize = 0;
for (ab = list_prev(dev->l2ad_buflist, head); ab;
ab = list_prev(dev->l2ad_buflist, ab)) {
l2arc_buf_hdr_t *l2hdr;
Expand Down Expand Up @@ -5172,7 +5181,7 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,

/* Compression may have squashed the buffer to zero length. */
if (buf_sz != 0) {
uint64_t buf_p_sz;
uint64_t buf_a_sz;

wzio = zio_write_phys(pio, dev->l2ad_vdev,
dev->l2ad_hand, buf_sz, buf_data, ZIO_CHECKSUM_OFF,
Expand All @@ -5183,13 +5192,12 @@ l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz,
zio_t *, wzio);
(void) zio_nowait(wzio);

write_asize += buf_sz;
/*
* Keep the clock hand suitably device-aligned.
*/
buf_p_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
write_psize += buf_p_sz;
dev->l2ad_hand += buf_p_sz;
buf_a_sz = vdev_psize_to_asize(dev->l2ad_vdev, buf_sz);
write_asize += buf_a_sz;
dev->l2ad_hand += buf_a_sz;
}
}

Expand Down Expand Up @@ -5252,12 +5260,6 @@ l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr)
csize = zio_compress_data(ZIO_COMPRESS_LZ4, l2hdr->b_tmp_cdata,
cdata, l2hdr->b_asize);

rounded = P2ROUNDUP(csize, (size_t)SPA_MINBLOCKSIZE);
if (rounded > csize) {
bzero((char *)cdata + csize, rounded - csize);
csize = rounded;
}

if (csize == 0) {
/* zero block, indicate that there's nothing to write */
zio_data_buf_free(cdata, len);
Expand All @@ -5266,11 +5268,19 @@ l2arc_compress_buf(l2arc_buf_hdr_t *l2hdr)
l2hdr->b_tmp_cdata = NULL;
ARCSTAT_BUMP(arcstat_l2_compress_zeros);
return (B_TRUE);
} else if (csize > 0 && csize < len) {
}

rounded = P2ROUNDUP(csize,
(size_t)1 << l2hdr->b_dev->l2ad_vdev->vdev_ashift);
if (rounded < len) {
/*
* Compression succeeded, we'll keep the cdata around for
* writing and release it afterwards.
*/
if (rounded > csize) {
bzero((char *)cdata + csize, rounded - csize);
csize = rounded;
}
l2hdr->b_compress = ZIO_COMPRESS_LZ4;
l2hdr->b_asize = csize;
l2hdr->b_tmp_cdata = cdata;
Expand Down