Author: kib
Date: Wed Mar 27 10:56:15 2013
New Revision: 248790
URL: http://svnweb.freebsd.org/changeset/base/248790
Log:
On i386, double the default size of the bio transient map. With the
maxbcache size fixed, the auto-tuned transient map is too small for
real-world load on i386.
Tested by: David Wolfskill
Sponsored by: The FreeBSD Foundation
Modified:
head/sys/kern/vfs_bio.c
Modified: head/sys/kern/vfs_bio.c
==============================================================================
--- head/sys/kern/vfs_bio.c Wed Mar 27 10:52:18 2013 (r248789)
+++ head/sys/kern/vfs_bio.c Wed Mar 27 10:56:15 2013 (r248790)
@@ -520,6 +520,12 @@ bd_speedup(void)
mtx_unlock(&bdlock);
}
+#ifdef __i386__
+#define TRANSIENT_DENOM 5
+#else
+#define TRANSIENT_DENOM 10
+#endif
+
/*
* Calculating buffer cache scaling values and reserve space for buffer
* headers. This is called during low level kernel initialization and
@@ -579,8 +585,8 @@ kern_vfs_bio_buffer_alloc(caddr_t v, lon
* to the amount of the buffer mapped for typical UFS load.
*
* Clip the buffer map to reserve space for the transient
- * BIOs, if its extent is bigger than 90% of the maximum
- * buffer map extent on the platform.
+ * BIOs, if its extent is bigger than 90% (80% on i386) of the
+ * maximum buffer map extent on the platform.
*
* The fall-back to the maxbuf in case of maxbcache unset,
* allows to not trim the buffer KVA for the architectures
@@ -589,7 +595,8 @@ kern_vfs_bio_buffer_alloc(caddr_t v, lon
if (bio_transient_maxcnt == 0 && unmapped_buf_allowed) {
maxbuf_sz = maxbcache != 0 ? maxbcache : maxbuf * BKVASIZE;
buf_sz = (long)nbuf * BKVASIZE;
- if (buf_sz < maxbuf_sz / 10 * 9) {
+ if (buf_sz < maxbuf_sz / TRANSIENT_DENOM *
+ (TRANSIENT_DENOM - 1)) {
/*
* There is more KVA than memory. Do not
* adjust buffer map size, and assign the rest
@@ -599,10 +606,10 @@ kern_vfs_bio_buffer_alloc(caddr_t v, lon
} else {
/*
* Buffer map spans all KVA we could afford on
- * this platform. Give 10% of the buffer map
- * to the transient bio map.
+ * this platform. Give 10% (20% on i386) of
+ * the buffer map to the transient bio map.
*/
- biotmap_sz = buf_sz / 10;
+ biotmap_sz = buf_sz / TRANSIENT_DENOM;
buf_sz -= biotmap_sz;
}
if (biotmap_sz / INT_MAX > MAXPHYS)
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