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IB/iser: Do not reduce max_sectors

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The iSER driver reduces max_sectors. For example, if you load the
ib_iser module with max_sectors=1024, you will see that
/sys/class/block/<bdev>/queue/max_hw_sectors_kb is 508. It is an
incorrect value. The expected value is (max_sectors * sector_size) /
1024 = 512.

Reducing of max_sectors can cause performance degradation due to
unnecessary splitting of IO requests.

The number of pages per MR has been fixed here, so there is no longer
any need to reduce max_sectors.

Fixes: 9c674815d3 ("IB/iser: Fix max_sectors calculation")
Signed-off-by: Sergey Gorenko <sergeygo@mellanox.com>
Reviewed-by: Israel Rukshin <israelr@mellanox.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Acked-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Doug Ledford <dledford@redhat.com>
This commit is contained in:
Sergey Gorenko
2018-05-21 18:55:53 +03:00
committed by Doug Ledford
parent 01298c0cd4
commit 434dda422c
4 changed files with 26 additions and 11 deletions
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12
drivers/infiniband/ulp/iser/iscsi_iser.c
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@@ -665,19 +665,17 @@ iscsi_iser_session_create(struct iscsi_endpoint *ep,
goto free_host;
}
/*
* FRs or FMRs can only map up to a (device) page per entry, but if the
* first entry is misaligned we'll end up using using two entries
* (head and tail) for a single page worth data, so we have to drop
* one segment from the calculation.
*/
max_fr_sectors = ((shost->sg_tablesize - 1) * PAGE_SIZE) >> 9;
max_fr_sectors = (shost->sg_tablesize * PAGE_SIZE) >> 9;
shost->max_sectors = min(iser_max_sectors, max_fr_sectors);
iser_dbg("iser_conn %p, sg_tablesize %u, max_sectors %u\n",
iser_conn, shost->sg_tablesize,
shost->max_sectors);
if (shost->max_sectors < iser_max_sectors)
iser_warn("max_sectors was reduced from %u to %u\n",
iser_max_sectors, shost->max_sectors);
if (cmds_max > max_cmds) {
iser_info("cmds_max changed from %u to %u\n",
cmds_max, max_cmds);