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xen-devel
[Xen-devel] Re: [PATCH] xen-mapcache: Fix rlimit set size.
On 08/01/2011 09:26 PM, Anthony PERARD wrote:
Previously, the address space soft limit was set mcache_max_size. So,
before the mcache_max_size was reached by the mapcache, QEMU was killed
for overuse of the virtual address space.
This patch fix that by setting the soft limit to mcache_max_size + 80MB.
I observed that QEMU use 75MB more than max_mcache_size after several
empirical tests.
Not sure I understand. What are those 75MB?
Alex
Signed-off-by: Anthony PERARD<anthony.perard@xxxxxxxxxx>
---
xen-mapcache.c | 13 ++++++++++---
1 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/xen-mapcache.c b/xen-mapcache.c
index 007136a..40212f7 100644
--- a/xen-mapcache.c
+++ b/xen-mapcache.c
@@ -40,6 +40,13 @@
#endif
#define MCACHE_BUCKET_SIZE (1UL<< MCACHE_BUCKET_SHIFT)
+/* This is the size of the virtual address space reserve to QEMU that will not
+ * be use by MapCache.
+ * From empirical tests I observed that qemu use 75MB more than the
+ * max_mcache_size.
+ */
+#define NON_MCACHE_MEMORY_SIZE (80 * 1024 * 1024)
+
#define mapcache_lock() ((void)0)
#define mapcache_unlock() ((void)0)
@@ -93,14 +100,14 @@ void xen_map_cache_init(void)
mapcache->last_address_index = -1;
getrlimit(RLIMIT_AS,&rlimit_as);
- if (rlimit_as.rlim_max< MCACHE_MAX_SIZE) {
+ if (rlimit_as.rlim_max< MCACHE_MAX_SIZE + NON_MCACHE_MEMORY_SIZE) {
rlimit_as.rlim_cur = rlimit_as.rlim_max;
} else {
- rlimit_as.rlim_cur = MCACHE_MAX_SIZE;
+ rlimit_as.rlim_cur = MCACHE_MAX_SIZE + NON_MCACHE_MEMORY_SIZE;
}
setrlimit(RLIMIT_AS,&rlimit_as);
- mapcache->max_mcache_size = rlimit_as.rlim_cur;
+ mapcache->max_mcache_size = rlimit_as.rlim_cur - NON_MCACHE_MEMORY_SIZE;
mapcache->nr_buckets =
(((mapcache->max_mcache_size>> XC_PAGE_SHIFT) +
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