cgroup: don't bother to resize pid array
When we open cgroup.procs, we'll allocate an buffer and store all tasks'
tgid in it, and then duplicate entries will be stripped. If that results
in a much smaller pid list, we'll re-allocate a smaller buffer.
But we've already sucessfully allocated memory and reading the procs
file is a short period and the memory will be freed very soon, so why
bother to re-allocate memory.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 49297cb..29c77a7 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3400,35 +3400,14 @@
else
kfree(p);
}
-static void *pidlist_resize(void *p, int newcount)
-{
- void *newlist;
- /* note: if new alloc fails, old p will still be valid either way */
- if (is_vmalloc_addr(p)) {
- newlist = vmalloc(newcount * sizeof(pid_t));
- if (!newlist)
- return NULL;
- memcpy(newlist, p, newcount * sizeof(pid_t));
- vfree(p);
- } else {
- newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
- }
- return newlist;
-}
/*
* pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
- * If the new stripped list is sufficiently smaller and there's enough memory
- * to allocate a new buffer, will let go of the unneeded memory. Returns the
- * number of unique elements.
+ * Returns the number of unique elements.
*/
-/* is the size difference enough that we should re-allocate the array? */
-#define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
-static int pidlist_uniq(pid_t **p, int length)
+static int pidlist_uniq(pid_t *list, int length)
{
int src, dest = 1;
- pid_t *list = *p;
- pid_t *newlist;
/*
* we presume the 0th element is unique, so i starts at 1. trivial
@@ -3449,16 +3428,6 @@
dest++;
}
after:
- /*
- * if the length difference is large enough, we want to allocate a
- * smaller buffer to save memory. if this fails due to out of memory,
- * we'll just stay with what we've got.
- */
- if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
- newlist = pidlist_resize(list, dest);
- if (newlist)
- *p = newlist;
- }
return dest;
}
@@ -3554,7 +3523,7 @@
/* now sort & (if procs) strip out duplicates */
sort(array, length, sizeof(pid_t), cmppid, NULL);
if (type == CGROUP_FILE_PROCS)
- length = pidlist_uniq(&array, length);
+ length = pidlist_uniq(array, length);
l = cgroup_pidlist_find(cgrp, type);
if (!l) {
pidlist_free(array);