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authorOmar Sandoval <osandov@fb.com>2018-08-21 21:55:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-22 10:52:46 -0700
commitbf991c2231117d50a7645792b514354fc8d19dae (patch)
treec7c74e6d467774e97be1a0022b26c1047a7465b8 /fs
parent37e949bd5293ddb70acf236eedf2ae8caa1db57b (diff)
downloadlinux-bf991c2231117d50a7645792b514354fc8d19dae.tar.bz2
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/fd346c11090cf93d867e01b8d73a6567c5ac6361.1531953780.git.osandov@fb.com Signed-off-by: Omar Sandoval <osandov@fb.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Bhupesh Sharma <bhsharma@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: James Morse <james.morse@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/kcore.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 808ef9afd084..758c14e46a44 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -428,10 +428,18 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
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) {