The patch titled
Subject: proc/kcore: optimize multiple page reads
has been added to the -mm tree. Its filename is
proc-kcore-optimize-multiple-page-reads.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-kcore-optimize-multiple-page-reads.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-kcore-optimize-multiple-page-reads.patch
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------------------------------------------------------
From: Omar Sandoval <osandov@xxxxxx>
Subject: proc/kcore: optimize multiple page reads
The current code does a full search of the segment list every time for
every page. This is wasteful, since it's almost certain that the next
page will be in the same segment. Instead, check if the previous segment
covers the current page before doing the list search.
Link: http://lkml.kernel.org/r/296622acfe01efc2e93472b312afe9e374370abe.1531440458.git.osandov@xxxxxx
Signed-off-by: Omar Sandoval <osandov@xxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN fs/proc/kcore.c~proc-kcore-optimize-multiple-page-reads fs/proc/kcore.c
--- a/fs/proc/kcore.c~proc-kcore-optimize-multiple-page-reads
+++ a/fs/proc/kcore.c
@@ -428,10 +428,18 @@ read_kcore(struct file *file, char __use
if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
tsz = buflen;
+ m = NULL;
while (buflen) {
- list_for_each_entry(m, &kclist_head, list) {
- if (start >= m->addr && start < (m->addr+m->size))
- break;
+ /*
+ * If this is the first iteration or the address is not within
+ * the previous entry, search for a matching entry.
+ */
+ if (!m || start < m->addr || start >= m->addr + m->size) {
+ list_for_each_entry(m, &kclist_head, list) {
+ if (start >= m->addr &&
+ start < m->addr + m->size)
+ break;
+ }
}
if (&m->list == &kclist_head) {
_
Patches currently in -mm which might be from osandov@xxxxxx are
proc-kcore-dont-grab-lock-for-kclist_add.patch
proc-kcore-replace-kclist_lock-rwlock-with-rwsem.patch
proc-kcore-fix-memory-hotplug-vs-multiple-opens-race.patch
proc-kcore-hold-lock-during-read.patch
proc-kcore-clean-up-elf-header-generation.patch
proc-kcore-optimize-multiple-page-reads.patch
proc-kcore-add-vmcoreinfo-note-to-proc-kcore.patch
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