From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
"Martin K . Petersen" <martin.petersen@oracle.com>,
linux-scsi@vger.kernel.org
Cc: Ming Lei <ming.lei@redhat.com>, Omar Sandoval <osandov@fb.com>,
Kashyap Desai <kashyap.desai@broadcom.com>,
Sumanesh Samanta <sumanesh.samanta@broadcom.com>,
"Ewan D . Milne" <emilne@redhat.com>,
Hannes Reinecke <hare@suse.de>
Subject: [PATCH V7 06/13] sbitmap: add helper of sbitmap_calculate_shift
Date: Fri, 22 Jan 2021 10:33:10 +0800 [thread overview]
Message-ID: <20210122023317.687987-7-ming.lei@redhat.com> (raw)
In-Reply-To: <20210122023317.687987-1-ming.lei@redhat.com>
Move code for calculating default shift into one public helper,
which can be used for SCSI to calculate shift.
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/sbitmap.h | 18 ++++++++++++++++++
lib/sbitmap.c | 16 +++-------------
2 files changed, 21 insertions(+), 13 deletions(-)
diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h
index c65ba887dcc3..3087e1f15fdd 100644
--- a/include/linux/sbitmap.h
+++ b/include/linux/sbitmap.h
@@ -332,6 +332,24 @@ static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr)
return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr));
}
+static inline int sbitmap_calculate_shift(unsigned int depth)
+{
+ int shift = ilog2(BITS_PER_LONG);
+
+ /*
+ * If the bitmap is small, shrink the number of bits per word so
+ * we spread over a few cachelines, at least. If less than 4
+ * bits, just forget about it, it's not going to work optimally
+ * anyway.
+ */
+ if (depth >= 4) {
+ while ((4U << shift) > depth)
+ shift--;
+ }
+
+ return shift;
+}
+
/**
* sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file.
* @sb: Bitmap to show.
diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 73da26ad021e..47b3691058eb 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -87,19 +87,9 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
unsigned int bits_per_word;
unsigned int i;
- if (shift < 0) {
- shift = ilog2(BITS_PER_LONG);
- /*
- * If the bitmap is small, shrink the number of bits per word so
- * we spread over a few cachelines, at least. If less than 4
- * bits, just forget about it, it's not going to work optimally
- * anyway.
- */
- if (depth >= 4) {
- while ((4U << shift) > depth)
- shift--;
- }
- }
+ if (shift < 0)
+ shift = sbitmap_calculate_shift(depth);
+
bits_per_word = 1U << shift;
if (bits_per_word > BITS_PER_LONG)
return -EINVAL;
--
2.28.0
next prev parent reply other threads:[~2021-01-22 2:37 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-22 2:33 [PATCH V7 00/13] blk-mq/scsi: tracking device queue depth via sbitmap Ming Lei
2021-01-22 2:33 ` [PATCH V7 01/13] sbitmap: remove sbitmap_clear_bit_unlock Ming Lei
2021-01-22 2:33 ` [PATCH V7 02/13] sbitmap: maintain allocation round_robin in sbitmap Ming Lei
2021-01-22 2:33 ` [PATCH V7 03/13] sbitmap: add helpers for updating allocation hint Ming Lei
2021-01-22 2:33 ` [PATCH V7 04/13] sbitmap: move allocation hint into sbitmap Ming Lei
2021-01-22 2:33 ` [PATCH V7 05/13] sbitmap: export sbitmap_weight Ming Lei
2021-01-22 2:33 ` Ming Lei [this message]
2021-01-22 2:33 ` [PATCH V7 07/13] blk-mq: add callbacks for storing & retrieving budget token Ming Lei
2021-01-22 2:33 ` [PATCH V7 08/13] blk-mq: return budget token from .get_budget callback Ming Lei
2021-01-22 2:33 ` [PATCH V7 09/13] scsi: put hot fields of scsi_host_template into one cacheline Ming Lei
2021-01-22 2:33 ` [PATCH V7 10/13] megaraid_sas: v2 replace sdev_busy with local counter Ming Lei
2021-01-22 2:33 ` [PATCH V7 11/13] scsi: add scsi_device_busy() to read sdev->device_busy Ming Lei
2021-01-22 2:33 ` [PATCH V7 12/13] scsi: make sure sdev->queue_depth is <= max(shost->can_queue, 1024) Ming Lei
2021-01-22 2:33 ` [PATCH V7 13/13] scsi: replace sdev->device_busy with sbitmap Ming Lei
2021-01-29 18:02 ` [PATCH V7 00/13] blk-mq/scsi: tracking device queue depth via sbitmap Martin K. Petersen
[not found] ` <20210131115245.GA1979183@T590>
2021-02-01 22:33 ` Martin K. Petersen
2021-02-03 11:14 ` Ming Lei
2021-02-04 2:59 ` Martin K. Petersen
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