Date: Sat, 07 Dec 2002 14:26:39 +0000 From: Ian Dowse <iedowse@maths.tcd.ie> To: Kirk McKusick <mckusick@beastie.mckusick.com> Cc: Brooks Davis <brooks@one-eyed-alien.net>, Nate Lawson <nate@root.org>, Archie Cobbs <archie@dellroad.org>, freebsd-current@FreeBSD.ORG Subject: Re: backgroud fsck is still locking up system (fwd) Message-ID: <200212071426.aa60667@salmon.maths.tcd.ie> In-Reply-To: Your message of "Fri, 06 Dec 2002 17:52:38 PST." <200212070152.gB71qc59094441@beastie.mckusick.com>
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In message <200212070152.gB71qc59094441@beastie.mckusick.com>, Kirk McKusick wr
ites:
>Adding a two minute delay before starting background fsck
>sounds like a very good idea to me. Please send me your
>suggested change.
BTW, I've been using a fsck_ffs modificaton for a while now that
does something like the disabled kernel I/O slowdown, but from
userland. It seems to help quite a lot in leaving some disk bandwidth
for other processes. Waiting a while before starting the fsck seems
like a good idea anyway though. Patch below (I think I posted an
earlier version of this before).
Ian
Index: fsutil.c
===================================================================
RCS file: /dump/FreeBSD-CVS/src/sbin/fsck_ffs/fsutil.c,v
retrieving revision 1.19
diff -u -r1.19 fsutil.c
--- fsutil.c 27 Nov 2002 02:18:57 -0000 1.19
+++ fsutil.c 4 Dec 2002 02:16:28 -0000
@@ -40,6 +40,7 @@
#endif /* not lint */
#include <sys/param.h>
+#include <sys/time.h>
#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/disklabel.h>
@@ -62,7 +63,13 @@
#include "fsck.h"
+static void slowio_start(void);
+static void slowio_end(void);
+
long diskreads, totalreads; /* Disk cache statistics */
+struct timeval slowio_starttime;
+int slowio_delay_usec = 10000; /* Initial IO delay for background fsck */
+int slowio_pollcnt;
int
ftypeok(union dinode *dp)
@@ -350,10 +357,15 @@
offset = blk;
offset *= dev_bsize;
+ if (bkgrdflag)
+ slowio_start();
if (lseek(fd, offset, 0) < 0)
rwerror("SEEK BLK", blk);
- else if (read(fd, buf, (int)size) == size)
+ else if (read(fd, buf, (int)size) == size) {
+ if (bkgrdflag)
+ slowio_end();
return (0);
+ }
rwerror("READ BLK", blk);
if (lseek(fd, offset, 0) < 0)
rwerror("SEEK BLK", blk);
@@ -463,6 +475,39 @@
idesc.id_blkno = blkno;
idesc.id_numfrags = frags;
(void)pass4check(&idesc);
+}
+
+/* Slow down IO so as to leave some disk bandwidth for other processes */
+void
+slowio_start()
+{
+
+ /* Delay one in every 8 operations by 16 times the average IO delay */
+ slowio_pollcnt = (slowio_pollcnt + 1) & 7;
+ if (slowio_pollcnt == 0) {
+ usleep(slowio_delay_usec * 16);
+ gettimeofday(&slowio_starttime, NULL);
+ }
+}
+
+void
+slowio_end()
+{
+ struct timeval tv;
+ int delay_usec;
+
+ if (slowio_pollcnt != 0)
+ return;
+
+ /* Update the slowdown interval. */
+ gettimeofday(&tv, NULL);
+ delay_usec = (tv.tv_sec - slowio_starttime.tv_sec) * 1000000 +
+ (tv.tv_usec - slowio_starttime.tv_usec);
+ if (delay_usec < 64)
+ delay_usec = 64;
+ if (delay_usec > 1000000)
+ delay_usec = 1000000;
+ slowio_delay_usec = (slowio_delay_usec * 63 + delay_usec) >> 6;
}
/*
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