[src/trunk]: src/sys/kern Try to coalesce writes to the journal in MAXPHYS si...

[hannken <hannken%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/45b9b69123c9
branches:  trunk
changeset: 783155:45b9b69123c9
user:      hannken <hannken%NetBSD.org@localhost>
date:      Sat Dec 08 07:24:42 2012 +0000

description:
Try to coalesce writes to the journal in MAXPHYS sized and aligned blocks.
Speeds up wapbl_flush() on raid5 by a factor of 3-4.

Discussed on tech-kern.

Needs pullup to NetBSD-6.

diffstat:

 sys/kern/vfs_wapbl.c |  100 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 95 insertions(+), 5 deletions(-)

diffs (177 lines):

diff -r 9ee7560d46d8 -r 45b9b69123c9 sys/kern/vfs_wapbl.c
--- a/sys/kern/vfs_wapbl.c      Sat Dec 08 07:05:23 2012 +0000
+++ b/sys/kern/vfs_wapbl.c      Sat Dec 08 07:24:42 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_wapbl.c,v 1.53 2012/11/17 10:10:17 hannken Exp $   */
+/*     $NetBSD: vfs_wapbl.c,v 1.54 2012/12/08 07:24:42 hannken Exp $   */
 
 /*-
  * Copyright (c) 2003, 2008, 2009 The NetBSD Foundation, Inc.
@@ -36,7 +36,7 @@
 #define WAPBL_INTERNAL
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_wapbl.c,v 1.53 2012/11/17 10:10:17 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_wapbl.c,v 1.54 2012/12/08 07:24:42 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/bitops.h>
@@ -184,6 +184,10 @@
 
        SIMPLEQ_HEAD(, wapbl_entry) wl_entries; /* On disk transaction
                                                   accounting */
+
+       u_char *wl_buffer;      /* l:   buffer for wapbl_buffered_write() */
+       daddr_t wl_buffer_dblk; /* l:   buffer disk block address */
+       size_t wl_buffer_used;  /* l:   buffer current use */
 };
 
 #ifdef WAPBL_DEBUG_PRINT
@@ -489,6 +493,9 @@
        wl->wl_dealloclens = wapbl_alloc(sizeof(*wl->wl_dealloclens) *
            wl->wl_dealloclim);
 
+       wl->wl_buffer = wapbl_alloc(MAXPHYS);
+       wl->wl_buffer_used = 0;
+
        wapbl_inodetrk_init(wl, WAPBL_INODETRK_SIZE);
 
        /* Initialize the commit header */
@@ -537,6 +544,7 @@
            sizeof(*wl->wl_deallocblks) * wl->wl_dealloclim);
        wapbl_free(wl->wl_dealloclens,
            sizeof(*wl->wl_dealloclens) * wl->wl_dealloclim);
+       wapbl_free(wl->wl_buffer, MAXPHYS);
        wapbl_inodetrk_free(wl);
        wapbl_free(wl, sizeof(*wl));
 
@@ -716,6 +724,7 @@
            sizeof(*wl->wl_deallocblks) * wl->wl_dealloclim);
        wapbl_free(wl->wl_dealloclens,
            sizeof(*wl->wl_dealloclens) * wl->wl_dealloclim);
+       wapbl_free(wl->wl_buffer, MAXPHYS);
        wapbl_inodetrk_free(wl);
 
        cv_destroy(&wl->wl_reclaimable_cv);
@@ -791,6 +800,81 @@
 }
 
 /*
+ * Flush buffered data if any.
+ */
+static int
+wapbl_buffered_flush(struct wapbl *wl)
+{
+       int error;
+
+       if (wl->wl_buffer_used == 0)
+               return 0;
+
+       error = wapbl_doio(wl->wl_buffer, wl->wl_buffer_used,
+           wl->wl_devvp, wl->wl_buffer_dblk, B_WRITE);
+       wl->wl_buffer_used = 0;
+
+       return error;
+}
+
+/*
+ * Write data to the log.
+ * Try to coalesce writes and emit MAXPHYS aligned blocks.
+ */
+static int
+wapbl_buffered_write(void *data, size_t len, struct wapbl *wl, daddr_t pbn)
+{
+       int error;
+       size_t resid;
+
+       /*
+        * If not adjacent to buffered data flush first.  Disk block
+        * address is always valid for non-empty buffer.
+        */
+       if (wl->wl_buffer_used > 0 &&
+           pbn != wl->wl_buffer_dblk + btodb(wl->wl_buffer_used)) {
+               error = wapbl_buffered_flush(wl);
+               if (error)
+                       return error;
+       }
+       /*
+        * If this write goes to an empty buffer we have to
+        * save the disk block address first.
+        */
+       if (wl->wl_buffer_used == 0)
+               wl->wl_buffer_dblk = pbn;
+       /*
+        * Remaining space so this buffer ends on a MAXPHYS boundary.
+        *
+        * Cannot become less or equal zero as the buffer would have been
+        * flushed on the last call then.
+        */
+       resid = MAXPHYS - dbtob(wl->wl_buffer_dblk % btodb(MAXPHYS)) -
+           wl->wl_buffer_used;
+       KASSERT(resid > 0);
+       KASSERT(dbtob(btodb(resid)) == resid);
+       if (len >= resid) {
+               memcpy(wl->wl_buffer + wl->wl_buffer_used, data, resid);
+               wl->wl_buffer_used += resid;
+               error = wapbl_doio(wl->wl_buffer, wl->wl_buffer_used,
+                   wl->wl_devvp, wl->wl_buffer_dblk, B_WRITE);
+               data = (uint8_t *)data + resid;
+               len -= resid;
+               wl->wl_buffer_dblk = pbn + btodb(resid);
+               wl->wl_buffer_used = 0;
+               if (error)
+                       return error;
+       }
+       KASSERT(len < MAXPHYS);
+       if (len > 0) {
+               memcpy(wl->wl_buffer + wl->wl_buffer_used, data, len);
+               wl->wl_buffer_used += len;
+       }
+
+       return 0;
+}
+
+/*
  * Off is byte offset returns new offset for next write
  * handles log wraparound
  */
@@ -813,7 +897,7 @@
 #ifdef _KERNEL
                pbn = btodb(pbn << wl->wl_log_dev_bshift);
 #endif
-               error = wapbl_write(data, slen, wl->wl_devvp, pbn);
+               error = wapbl_buffered_write(data, slen, wl, pbn);
                if (error)
                        return error;
                data = (uint8_t *)data + slen;
@@ -824,7 +908,7 @@
 #ifdef _KERNEL
        pbn = btodb(pbn << wl->wl_log_dev_bshift);
 #endif
-       error = wapbl_write(data, len, wl->wl_devvp, pbn);
+       error = wapbl_buffered_write(data, len, wl, pbn);
        if (error)
                return error;
        off += len;
@@ -1967,6 +2051,9 @@
        int error;
        daddr_t pbn;
 
+       error = wapbl_buffered_flush(wl);
+       if (error)
+               return error;
        /*
         * flush disk cache to ensure that blocks we've written are actually
         * written to the stable storage before the commit header.
@@ -1998,7 +2085,10 @@
 #ifdef _KERNEL
        pbn = btodb(pbn << wc->wc_log_dev_bshift);
 #endif
-       error = wapbl_write(wc, wc->wc_len, wl->wl_devvp, pbn);
+       error = wapbl_buffered_write(wc, wc->wc_len, wl, pbn);
+       if (error)
+               return error;
+       error = wapbl_buffered_flush(wl);
        if (error)
                return error;