nfs_congestion_kb is to control the max allowed writeback and in-commit
pages. It's not reasonable for them to outnumber dirty and to-commit
pages. So each of them should not take more than 1/4 dirty threshold.
Considering that nfs_init_writepagecache() is called on fresh boot,
at the time dirty_thresh is much higher than the real dirty limit after
lots of user space memory consumptions, use 1/8 instead.
Feng: fix deadlock by preventing (nfs_congestion_kb == 0)
CC: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
fs/nfs/write.c | 36 +++++++++++++++++-------------------
mm/page-writeback.c | 6 ++++++
2 files changed, 23 insertions(+), 19 deletions(-)
--- linux-next.orig/fs/nfs/write.c 2011-10-20 23:45:59.000000000 +0800
+++ linux-next/fs/nfs/write.c 2011-10-20 23:53:16.000000000 +0800
@@ -1782,6 +1782,22 @@ out:
}
#endif
+void nfs_update_congestion_thresh(void)
+{
+ unsigned long background_thresh;
+ unsigned long dirty_thresh;
+
+ /*
+ * Limit to 1/8 dirty threshold, so that writeback+in_commit pages
+ * won't overnumber dirty+to_commit pages.
+ */
+ global_dirty_limits(&background_thresh, &dirty_thresh);
+ dirty_thresh <<= PAGE_SHIFT - 10;
+ dirty_thresh += 1024;
+
+ nfs_congestion_kb = dirty_thresh / 8;
+}
+
int __init nfs_init_writepagecache(void)
{
nfs_wdata_cachep = kmem_cache_create("nfs_write_data",
@@ -1801,25 +1817,7 @@ int __init nfs_init_writepagecache(void)
if (nfs_commit_mempool == NULL)
return -ENOMEM;
- /*
- * NFS congestion size, scale with available memory.
- *
- * 64MB: 8192k
- * 128MB: 11585k
- * 256MB: 16384k
- * 512MB: 23170k
- * 1GB: 32768k
- * 2GB: 46340k
- * 4GB: 65536k
- * 8GB: 92681k
- * 16GB: 131072k
- *
- * This allows larger machines to have larger/more transfers.
- * Limit the default to 256M
- */
- nfs_congestion_kb = (16*int_sqrt(totalram_pages)) << (PAGE_SHIFT-10);
- if (nfs_congestion_kb > 256*1024)
- nfs_congestion_kb = 256*1024;
+ nfs_update_congestion_thresh();
return 0;
}
--- linux-next.orig/mm/page-writeback.c 2011-10-20 23:45:23.000000000 +0800
+++ linux-next/mm/page-writeback.c 2011-10-20 23:48:07.000000000 +0800
@@ -207,6 +207,10 @@ static int calc_period_shift(void)
return 2 + ilog2(dirty_total - 1);
}
+void __weak nfs_update_congestion_thresh(void)
+{
+}
+
/*
* update the period when the dirty threshold changes.
*/
@@ -217,6 +221,7 @@ static void update_completion_period(voi
prop_change_shift(&vm_dirties, shift);
writeback_set_ratelimit();
+ nfs_update_congestion_thresh();
}
int dirty_background_ratio_handler(struct ctl_table *table, int write,
@@ -447,6 +452,7 @@ unsigned long bdi_dirty_limit(struct bac
return bdi_dirty;
}
+EXPORT_SYMBOL_GPL(global_dirty_limits);
/*
* Dirty position control.
--
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