From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Lieven <pl@kamp.de>, qemu-devel@nongnu.org
Cc: kwolf@redhat.com, ronniesahlberg@gmail.com, stefanha@redhat.com
Subject: Re: [Qemu-devel] [RFC PATCH] block/iscsi: speed up read for unallocated sectors
Date: Mon, 24 Mar 2014 16:44:26 +0100 [thread overview]
Message-ID: <533052DA.9010209@redhat.com> (raw)
In-Reply-To: <1395675241-18859-1-git-send-email-pl@kamp.de>
Il 24/03/2014 16:34, Peter Lieven ha scritto:
> this patch implements a cache that tracks if a page on the
> iscsi target is allocated or not. The cache is implemented in
> a way that it allows for false positives
> (e.g. pretending a page is allocated, but it isn't), but
> no false negatives.
>
> The cached allocation info is then used to speed up the
> read process for unallocated sectors by issueing a GET_LBA_STATUS
> request for all sectors that are not yet known to be allocated.
> If the read request is confirmed to fall into an unallocated
> range we directly return zeroes and do not transfer the
> data over the wire.
>
> Tests have shown that a relatively small amount of GET_LBA_STATUS
> requests happens a vServer boot time to fill the allocation cache
> (all those blocks are not queried again).
>
> Not to transfer all the data of unallocated sectors saves a lot
> of time, bandwidth and storage I/O load during block jobs or storage
> migration and it saves a lot of bandwidth as well for any big sequential
> read of the whole disk (e.g. block copy or speed tests) if a significant
> number of blocks is unallocated.
>
> Signed-off-by: Peter Lieven <pl@kamp.de>
Nice---but this should only be done if BDRV_O_NOCACHE is clear.
Paolo
> ---
> block/iscsi.c | 281 ++++++++++++++++++++++++++++++++++++---------------------
> 1 file changed, 179 insertions(+), 102 deletions(-)
>
> diff --git a/block/iscsi.c b/block/iscsi.c
> index b490e98..72f0f58 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -30,6 +30,8 @@
> #include "qemu-common.h"
> #include "qemu/config-file.h"
> #include "qemu/error-report.h"
> +#include "qemu/bitops.h"
> +#include "qemu/bitmap.h"
> #include "block/block_int.h"
> #include "trace.h"
> #include "block/scsi.h"
> @@ -59,6 +61,8 @@ typedef struct IscsiLun {
> struct scsi_inquiry_logical_block_provisioning lbp;
> struct scsi_inquiry_block_limits bl;
> unsigned char *zeroblock;
> + unsigned long *allocationmap;
> + int cluster_sectors;
> } IscsiLun;
>
> typedef struct IscsiTask {
> @@ -91,6 +95,7 @@ typedef struct IscsiAIOCB {
> #define NOP_INTERVAL 5000
> #define MAX_NOP_FAILURES 3
> #define ISCSI_CMD_RETRIES 5
> +#define ISCSI_CHECKALLOC_THRES 63
>
> static void
> iscsi_bh_cb(void *p)
> @@ -273,6 +278,22 @@ static bool is_request_lun_aligned(int64_t sector_num, int nb_sectors,
> return 1;
> }
>
> +static void iscsi_allocationmap_set(IscsiLun *iscsilun, int64_t sector_num, int nb_sectors) {
> + if (!iscsilun->cluster_sectors) {
> + return;
> + }
> + bitmap_set(iscsilun->allocationmap, sector_num / iscsilun->cluster_sectors,
> + DIV_ROUND_UP(nb_sectors, iscsilun->cluster_sectors));
> +}
> +
> +static void iscsi_allocationmap_clear(IscsiLun *iscsilun, int64_t sector_num, int nb_sectors) {
> + if (!iscsilun->cluster_sectors) {
> + return;
> + }
> + bitmap_clear(iscsilun->allocationmap, sector_num / iscsilun->cluster_sectors,
> + DIV_ROUND_UP(nb_sectors, iscsilun->cluster_sectors));
> +}
> +
> static int coroutine_fn iscsi_co_writev(BlockDriverState *bs,
> int64_t sector_num, int nb_sectors,
> QEMUIOVector *iov)
> @@ -336,9 +357,120 @@ retry:
> return -EIO;
> }
>
> + iscsi_allocationmap_set(iscsilun, sector_num, nb_sectors);
> +
> return 0;
> }
>
> +
> +static bool iscsi_allocationmap_is_allocated(IscsiLun *iscsilun, int64_t sector_num, int nb_sectors) {
> + unsigned long size = DIV_ROUND_UP(sector_num + nb_sectors, iscsilun->cluster_sectors);
> +
> + if (!iscsilun->cluster_sectors) {
> + return true;
> + }
> +
> + return !(find_next_bit(iscsilun->allocationmap, size,
> + sector_num / iscsilun->cluster_sectors) == size);
> +}
> +
> +
> +#if defined(LIBISCSI_FEATURE_IOVECTOR)
> +
> +static int64_t coroutine_fn iscsi_co_get_block_status(BlockDriverState *bs,
> + int64_t sector_num,
> + int nb_sectors, int *pnum)
> +{
> + IscsiLun *iscsilun = bs->opaque;
> + struct scsi_get_lba_status *lbas = NULL;
> + struct scsi_lba_status_descriptor *lbasd = NULL;
> + struct IscsiTask iTask;
> + int64_t ret;
> +
> + iscsi_co_init_iscsitask(iscsilun, &iTask);
> +
> + if (!is_request_lun_aligned(sector_num, nb_sectors, iscsilun)) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + /* default to all sectors allocated */
> + ret = BDRV_BLOCK_DATA;
> + ret |= (sector_num << BDRV_SECTOR_BITS) | BDRV_BLOCK_OFFSET_VALID;
> + *pnum = nb_sectors;
> +
> + /* LUN does not support logical block provisioning */
> + if (iscsilun->lbpme == 0) {
> + goto out;
> + }
> +
> +retry:
> + if (iscsi_get_lba_status_task(iscsilun->iscsi, iscsilun->lun,
> + sector_qemu2lun(sector_num, iscsilun),
> + 8 + 16, iscsi_co_generic_cb,
> + &iTask) == NULL) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + while (!iTask.complete) {
> + iscsi_set_events(iscsilun);
> + qemu_coroutine_yield();
> + }
> +
> + if (iTask.do_retry) {
> + if (iTask.task != NULL) {
> + scsi_free_scsi_task(iTask.task);
> + iTask.task = NULL;
> + }
> + iTask.complete = 0;
> + goto retry;
> + }
> +
> + if (iTask.status != SCSI_STATUS_GOOD) {
> + /* in case the get_lba_status_callout fails (i.e.
> + * because the device is busy or the cmd is not
> + * supported) we pretend all blocks are allocated
> + * for backwards compatibility */
> + goto out;
> + }
> +
> + lbas = scsi_datain_unmarshall(iTask.task);
> + if (lbas == NULL) {
> + ret = -EIO;
> + goto out;
> + }
> +
> + lbasd = &lbas->descriptors[0];
> +
> + if (sector_qemu2lun(sector_num, iscsilun) != lbasd->lba) {
> + ret = -EIO;
> + goto out;
> + }
> +
> + *pnum = sector_lun2qemu(lbasd->num_blocks, iscsilun);
> + if (*pnum > nb_sectors) {
> + *pnum = nb_sectors;
> + }
> +
> + if (lbasd->provisioning == SCSI_PROVISIONING_TYPE_DEALLOCATED ||
> + lbasd->provisioning == SCSI_PROVISIONING_TYPE_ANCHORED) {
> + ret &= ~BDRV_BLOCK_DATA;
> + if (iscsilun->lbprz) {
> + ret |= BDRV_BLOCK_ZERO;
> + }
> + }
> +
> +out:
> + if (iTask.task != NULL) {
> + scsi_free_scsi_task(iTask.task);
> + }
> + return ret;
> +}
> +
> +#endif /* LIBISCSI_FEATURE_IOVECTOR */
> +
> +
> static int coroutine_fn iscsi_co_readv(BlockDriverState *bs,
> int64_t sector_num, int nb_sectors,
> QEMUIOVector *iov)
> @@ -355,6 +487,27 @@ static int coroutine_fn iscsi_co_readv(BlockDriverState *bs,
> return -EINVAL;
> }
>
> +#if defined(LIBISCSI_FEATURE_IOVECTOR)
> + if (iscsilun->lbprz && nb_sectors > ISCSI_CHECKALLOC_THRES &&
> + !iscsi_allocationmap_is_allocated(iscsilun, sector_num, nb_sectors)) {
> + int64_t ret;
> + int pnum;
> + ret = iscsi_co_get_block_status(bs, sector_num, INT_MAX, &pnum);
> + if (ret < 0) {
> + return ret;
> + }
> + if (ret & BDRV_BLOCK_ZERO) {
> + iscsi_allocationmap_clear(iscsilun, sector_num, pnum);
> + if (pnum >= nb_sectors) {
> + qemu_iovec_memset(iov, 0, 0x00, iov->size);
> + return 0;
> + }
> + } else {
> + iscsi_allocationmap_set(iscsilun, sector_num, pnum);
> + }
> + }
> +#endif
> +
> lba = sector_qemu2lun(sector_num, iscsilun);
> num_sectors = sector_qemu2lun(nb_sectors, iscsilun);
>
> @@ -639,101 +792,6 @@ iscsi_getlength(BlockDriverState *bs)
> return len;
> }
>
> -#if defined(LIBISCSI_FEATURE_IOVECTOR)
> -
> -static int64_t coroutine_fn iscsi_co_get_block_status(BlockDriverState *bs,
> - int64_t sector_num,
> - int nb_sectors, int *pnum)
> -{
> - IscsiLun *iscsilun = bs->opaque;
> - struct scsi_get_lba_status *lbas = NULL;
> - struct scsi_lba_status_descriptor *lbasd = NULL;
> - struct IscsiTask iTask;
> - int64_t ret;
> -
> - iscsi_co_init_iscsitask(iscsilun, &iTask);
> -
> - if (!is_request_lun_aligned(sector_num, nb_sectors, iscsilun)) {
> - ret = -EINVAL;
> - goto out;
> - }
> -
> - /* default to all sectors allocated */
> - ret = BDRV_BLOCK_DATA;
> - ret |= (sector_num << BDRV_SECTOR_BITS) | BDRV_BLOCK_OFFSET_VALID;
> - *pnum = nb_sectors;
> -
> - /* LUN does not support logical block provisioning */
> - if (iscsilun->lbpme == 0) {
> - goto out;
> - }
> -
> -retry:
> - if (iscsi_get_lba_status_task(iscsilun->iscsi, iscsilun->lun,
> - sector_qemu2lun(sector_num, iscsilun),
> - 8 + 16, iscsi_co_generic_cb,
> - &iTask) == NULL) {
> - ret = -ENOMEM;
> - goto out;
> - }
> -
> - while (!iTask.complete) {
> - iscsi_set_events(iscsilun);
> - qemu_coroutine_yield();
> - }
> -
> - if (iTask.do_retry) {
> - if (iTask.task != NULL) {
> - scsi_free_scsi_task(iTask.task);
> - iTask.task = NULL;
> - }
> - iTask.complete = 0;
> - goto retry;
> - }
> -
> - if (iTask.status != SCSI_STATUS_GOOD) {
> - /* in case the get_lba_status_callout fails (i.e.
> - * because the device is busy or the cmd is not
> - * supported) we pretend all blocks are allocated
> - * for backwards compatibility */
> - goto out;
> - }
> -
> - lbas = scsi_datain_unmarshall(iTask.task);
> - if (lbas == NULL) {
> - ret = -EIO;
> - goto out;
> - }
> -
> - lbasd = &lbas->descriptors[0];
> -
> - if (sector_qemu2lun(sector_num, iscsilun) != lbasd->lba) {
> - ret = -EIO;
> - goto out;
> - }
> -
> - *pnum = sector_lun2qemu(lbasd->num_blocks, iscsilun);
> - if (*pnum > nb_sectors) {
> - *pnum = nb_sectors;
> - }
> -
> - if (lbasd->provisioning == SCSI_PROVISIONING_TYPE_DEALLOCATED ||
> - lbasd->provisioning == SCSI_PROVISIONING_TYPE_ANCHORED) {
> - ret &= ~BDRV_BLOCK_DATA;
> - if (iscsilun->lbprz) {
> - ret |= BDRV_BLOCK_ZERO;
> - }
> - }
> -
> -out:
> - if (iTask.task != NULL) {
> - scsi_free_scsi_task(iTask.task);
> - }
> - return ret;
> -}
> -
> -#endif /* LIBISCSI_FEATURE_IOVECTOR */
> -
> static int
> coroutine_fn iscsi_co_discard(BlockDriverState *bs, int64_t sector_num,
> int nb_sectors)
> @@ -859,6 +917,12 @@ retry:
> return -EIO;
> }
>
> + if (flags & BDRV_REQ_MAY_UNMAP) {
> + iscsi_allocationmap_clear(iscsilun, sector_num, nb_sectors);
> + } else {
> + iscsi_allocationmap_set(iscsilun, sector_num, nb_sectors);
> + }
> +
> return 0;
> }
>
> @@ -1288,6 +1352,19 @@ static int iscsi_open(BlockDriverState *bs, QDict *options, int flags,
> timer_mod(iscsilun->nop_timer, qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + NOP_INTERVAL);
> #endif
>
> + /* Guess the internal cluster (page) size of the iscsi target by the means
> + * of opt_unmap_gran. Transfer the unmap granularity only if it has a
> + * reasonable size */
> + if (iscsilun->bl.opt_unmap_gran * iscsilun->block_size >= 64 * 1024 &&
> + iscsilun->bl.opt_unmap_gran * iscsilun->block_size <= 16 * 1024 * 1024) {
> + iscsilun->cluster_sectors = (iscsilun->bl.opt_unmap_gran * iscsilun->block_size) >> BDRV_SECTOR_BITS;
> +#if defined(LIBISCSI_FEATURE_IOVECTOR)
> + if (iscsilun->lbprz) {
> + iscsilun->allocationmap = bitmap_new(DIV_ROUND_UP(bs->total_sectors, iscsilun->cluster_sectors));
> + }
> +#endif
> + }
> +
> out:
> qemu_opts_del(opts);
> if (initiator_name != NULL) {
> @@ -1321,6 +1398,7 @@ static void iscsi_close(BlockDriverState *bs)
> qemu_aio_set_fd_handler(iscsi_get_fd(iscsi), NULL, NULL, NULL);
> iscsi_destroy_context(iscsi);
> g_free(iscsilun->zeroblock);
> + g_free(iscsilun->allocationmap);
> memset(iscsilun, 0, sizeof(IscsiLun));
> }
>
> @@ -1379,6 +1457,11 @@ static int iscsi_truncate(BlockDriverState *bs, int64_t offset)
> return -EINVAL;
> }
>
> + if (iscsilun->allocationmap) {
> + g_free(iscsilun->allocationmap);
> + iscsilun->allocationmap = bitmap_new(DIV_ROUND_UP(bs->total_sectors, iscsilun->cluster_sectors));
> + }
> +
> return 0;
> }
>
> @@ -1441,13 +1524,7 @@ static int iscsi_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
> IscsiLun *iscsilun = bs->opaque;
> bdi->unallocated_blocks_are_zero = !!iscsilun->lbprz;
> bdi->can_write_zeroes_with_unmap = iscsilun->lbprz && iscsilun->lbp.lbpws;
> - /* Guess the internal cluster (page) size of the iscsi target by the means
> - * of opt_unmap_gran. Transfer the unmap granularity only if it has a
> - * reasonable size for bdi->cluster_size */
> - if (iscsilun->bl.opt_unmap_gran * iscsilun->block_size >= 64 * 1024 &&
> - iscsilun->bl.opt_unmap_gran * iscsilun->block_size <= 16 * 1024 * 1024) {
> - bdi->cluster_size = iscsilun->bl.opt_unmap_gran * iscsilun->block_size;
> - }
> + bdi->cluster_size = iscsilun->cluster_sectors * BDRV_SECTOR_SIZE;
> return 0;
> }
>
>
next prev parent reply other threads:[~2014-03-24 16:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-24 15:34 [Qemu-devel] [RFC PATCH] block/iscsi: speed up read for unallocated sectors Peter Lieven
2014-03-24 15:44 ` Paolo Bonzini [this message]
2014-03-24 16:28 ` Peter Lieven
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