[PATCH]: sysctl to tune async and sync bdflush triggers

From: Anton Blanchard (anton@linuxcare.com.au)
Date: Thu Dec 07 2000 - 00:15:54 EST


Hi,

At the moment the synchronous flush trigger for bdflush is hardwired to be
double the asynchronous one. This is a pain for people with lots of RAM.

This patch adds a new variable to the bdflush sysctl so both can be
tuned independently. It also sets the defaults to 40% and 80% for async and
sync flushing. This has worked fine on my test machines (128M RAM and 2G RAM).

btw: does anything still touch these dummy entries?

Cheers,
Anton

diff -urN linux/fs/buffer.c linux_intel/fs/buffer.c
--- linux/fs/buffer.c Thu Dec 7 11:24:40 2000
+++ linux_intel/fs/buffer.c Thu Dec 7 00:08:06 2000
@@ -122,16 +122,17 @@
                                   when trying to refill buffers. */
                 int interval; /* jiffies delay between kupdate flushes */
                 int age_buffer; /* Time for normal buffer to age before we flush it */
- int dummy1; /* unused, was age_super */
+ int nfract_sync; /* Percentage of buffer cache dirty to
+ activate bdflush synchronously */
                 int dummy2; /* unused */
                 int dummy3; /* unused */
         } b_un;
         unsigned int data[N_PARAM];
-} bdf_prm = {{40, 500, 64, 256, 5*HZ, 30*HZ, 5*HZ, 1884, 2}};
+} bdf_prm = {{40, 500, 64, 256, 5*HZ, 30*HZ, 80, 0, 0}};
 
 /* These are the min and max parameter values that we will allow to be assigned */
-int bdflush_min[N_PARAM] = { 0, 10, 5, 25, 0, 1*HZ, 1*HZ, 1, 1};
-int bdflush_max[N_PARAM] = {100,50000, 20000, 20000,600*HZ, 6000*HZ, 6000*HZ, 2047, 5};
+int bdflush_min[N_PARAM] = { 0, 10, 5, 25, 0, 1*HZ, 0, 0, 0};
+int bdflush_max[N_PARAM] = {100,50000, 20000, 20000,600*HZ, 6000*HZ, 100, 0, 0};
 
 /*
  * Rewrote the wait-routines to use the "new" wait-queue functionality,
@@ -1036,9 +1037,9 @@
         dirty = size_buffers_type[BUF_DIRTY] >> PAGE_SHIFT;
         tot = nr_free_buffer_pages();
 
- dirty *= 200;
+ dirty *= 100;
         soft_dirty_limit = tot * bdf_prm.b_un.nfract;
- hard_dirty_limit = soft_dirty_limit * 2;
+ hard_dirty_limit = tot * bdf_prm.b_un.nfract_sync;
 
         /* First, check for the "real" dirty limit. */
         if (dirty > soft_dirty_limit) {
-
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