81 lines
2.4 KiB
Diff
81 lines
2.4 KiB
Diff
From 26c6b9b99d8f8d7897687a2192be4920a44c1eff Mon Sep 17 00:00:00 2001
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From: Guillaume Morin <guillaume@morinfr.org>
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Date: Tue, 1 Nov 2016 22:41:22 +0100
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Subject: [PATCH 16/28] fix behavior while shrinking
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Adjust mapsize as we're unmapping pages. Do not lie to glibc about
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shrinking by less than a page. It's unnecessary because we are not
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giving back any memory to the kernel, but also it forces us to zero
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out this memory because morecore() assumes by default that "new"
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memory is already zero'd.
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Signed-off-by: Guillaume Morin <guillaume@morinfr.org>
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Signed-off-by: Eric B Munson <emunson@mgebm.net>
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---
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morecore.c | 37 +++++++++++++++++++++++++++----------
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1 file changed, 27 insertions(+), 10 deletions(-)
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diff --git a/morecore.c b/morecore.c
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index 62ad252..6563bbd 100644
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--- a/morecore.c
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+++ b/morecore.c
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@@ -178,20 +178,37 @@ static void *hugetlbfs_morecore(ptrdiff_t increment)
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if (ret) {
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WARNING("Unmapping failed while shrinking heap: "
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"%s\n", strerror(errno));
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- } else if (!__hugetlb_opts.map_hugetlb && !using_default_pagesize){
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-
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- /*
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- * Now shrink the hugetlbfs file.
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- */
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+ } else {
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mapsize += delta;
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- ret = ftruncate(heap_fd, mapsize);
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- if (ret) {
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- WARNING("Could not truncate hugetlbfs file to "
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- "shrink heap: %s\n", strerror(errno));
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+ /*
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+ * the glibc assumes by default that newly allocated
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+ * memory by morecore() will be zeroed. It would be
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+ * wasteful to do it for allocation so we only shrink
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+ * the top by the size of a page.
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+ */
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+ increment = heapbase - heaptop + mapsize;
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+
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+ if (!__hugetlb_opts.map_hugetlb && !using_default_pagesize){
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+
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+ /*
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+ * Now shrink the hugetlbfs file.
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+ */
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+ ret = ftruncate(heap_fd, mapsize);
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+ if (ret) {
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+ WARNING("Could not truncate hugetlbfs file to "
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+ "shrink heap: %s\n", strerror(errno));
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+ }
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}
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}
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}
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+ else if (increment < 0) {
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+ /* Don't shrink by less than a page to avoid having to zero
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+ * the memory. There is no point in lying to glibc since
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+ * we're not freeing any memory.
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+ */
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+ increment = 0;
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+ }
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/* heap is continuous */
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p = heaptop;
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@@ -355,7 +372,7 @@ void hugetlbfs_setup_morecore(void)
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/* Set some allocator options more appropriate for hugepages */
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if (__hugetlb_opts.shrink_ok)
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- mallopt(M_TRIM_THRESHOLD, hpage_size / 2);
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+ mallopt(M_TRIM_THRESHOLD, hpage_size + hpage_size / 2);
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else
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mallopt(M_TRIM_THRESHOLD, -1);
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mallopt(M_TOP_PAD, hpage_size / 2);
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--
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1.8.3.1
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