From: Wei Wang <wei.w.wang@intel.com>
To: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org,
qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org,
kvm@vger.kernel.org, linux-mm@kvack.org, mst@redhat.com,
mhocko@kernel.org, akpm@linux-foundation.org,
mawilcox@microsoft.com
Cc: david@redhat.com, penguin-kernel@I-love.SAKURA.ne.jp,
cornelia.huck@de.ibm.com, mgorman@techsingularity.net,
aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com,
willy@infradead.org, wei.w.wang@intel.com,
liliang.opensource@gmail.com, yang.zhang.wz@gmail.com,
quan.xu@aliyun.com, nilal@redhat.com, riel@redhat.com
Subject: [PATCH v18 04/10] xbitmap: potential improvement
Date: Wed, 29 Nov 2017 21:55:20 +0800 [thread overview]
Message-ID: <1511963726-34070-5-git-send-email-wei.w.wang@intel.com> (raw)
In-Reply-To: <1511963726-34070-1-git-send-email-wei.w.wang@intel.com>
This patch made some changes to the original xbitmap implementation from
the linux-dax tree:
- remove xb_fill() and xb_zero() from xbitmap.h since they are not
implemented;
- xb_test_bit: changed "ebit > BITS_PER_LONG" to "ebit >= BITS_PER_LONG",
because bit 64 beyonds the "unsigned long" exceptional entry (0 to 63);
- xb_set_bit: delete the new inserted radix_tree_node when failing to
get the per cpu ida bitmap, this avoids the kind of memory leak of the
unused radix tree node left in the tree.
- xb_clear_bit: change it to be a void function, since the original
implementation reurns nothing than a 0.
- remove the comment above "#define XB_INDEX_BITS", because it causes
confusion based on the feedbacks from the previous discussion;
- xb_preload: with the original implementation, the CPU that successfully
do __radix_tree_preload() may get into sleep by kmalloc(), which has a
risk of getting the caller of xb_preload() scheduled to another CPU
after waken up, and the new CPU may not have radix_tree_node
pre-allocated there, this will be a problem when inserting a node to
the tree later. This patch moves __radix_tree_preload() after kmalloc()
and returns a boolean to indicate the success or failure. Also, add the
__must_check annotation to xb_preload for prudence purpose.
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
include/linux/xbitmap.h | 5 +----
lib/radix-tree.c | 27 +++++++++++++++++++++------
lib/xbitmap.c | 24 +++++++++++++-----------
3 files changed, 35 insertions(+), 21 deletions(-)
diff --git a/include/linux/xbitmap.h b/include/linux/xbitmap.h
index ed75d87..b4d8375 100644
--- a/include/linux/xbitmap.h
+++ b/include/linux/xbitmap.h
@@ -36,15 +36,12 @@ int xb_set_bit(struct xb *xb, unsigned long bit);
bool xb_test_bit(const struct xb *xb, unsigned long bit);
int xb_clear_bit(struct xb *xb, unsigned long bit);
-int xb_zero(struct xb *xb, unsigned long start, unsigned long nbits);
-int xb_fill(struct xb *xb, unsigned long start, unsigned long nbits);
-
static inline bool xb_empty(const struct xb *xb)
{
return radix_tree_empty(&xb->xbrt);
}
-void xb_preload(gfp_t);
+bool xb_preload(gfp_t);
static inline void xb_preload_end(void)
{
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 7000ad6..a039588 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -77,9 +77,6 @@ static struct kmem_cache *radix_tree_node_cachep;
RADIX_TREE_MAP_SHIFT))
#define IDA_PRELOAD_SIZE (IDA_MAX_PATH * 2 - 1)
-/*
- * The XB can go up to unsigned long, but also uses a bitmap.
- */
#define XB_INDEX_BITS (BITS_PER_LONG - ilog2(IDA_BITMAP_BITS))
#define XB_MAX_PATH (DIV_ROUND_UP(XB_INDEX_BITS, \
RADIX_TREE_MAP_SHIFT))
@@ -2145,17 +2142,35 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
}
EXPORT_SYMBOL(ida_pre_get);
-void xb_preload(gfp_t gfp)
+/**
+ * xb_preload - preload for xb_set_bit()
+ * @gfp_mask: allocation mask to use for preloading
+ *
+ * Preallocate memory to use for the next call to xb_set_bit(). On success,
+ * return true, with preemption disabled. On error, return false with
+ * preemption not disabled.
+ */
+__must_check bool xb_preload(gfp_t gfp)
{
- __radix_tree_preload(gfp, XB_PRELOAD_SIZE);
if (!this_cpu_read(ida_bitmap)) {
struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);
if (!bitmap)
- return;
+ return false;
+ /*
+ * The per-CPU variable is updated with preemption enabled.
+ * If the calling task is unlucky to be scheduled to another
+ * CPU which has no ida_bitmap allocation, it will be detected
+ * when setting a bit (i.e. __xb_set_bit()).
+ */
bitmap = this_cpu_cmpxchg(ida_bitmap, NULL, bitmap);
kfree(bitmap);
}
+
+ if (__radix_tree_preload(gfp, XB_PRELOAD_SIZE) < 0)
+ return false;
+
+ return true;
}
EXPORT_SYMBOL(xb_preload);
diff --git a/lib/xbitmap.c b/lib/xbitmap.c
index 2b547a73..182aa29 100644
--- a/lib/xbitmap.c
+++ b/lib/xbitmap.c
@@ -39,8 +39,10 @@ int xb_set_bit(struct xb *xb, unsigned long bit)
return 0;
}
bitmap = this_cpu_xchg(ida_bitmap, NULL);
- if (!bitmap)
+ if (!bitmap) {
+ __radix_tree_delete(root, node, slot);
return -EAGAIN;
+ }
memset(bitmap, 0, sizeof(*bitmap));
bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
rcu_assign_pointer(*slot, bitmap);
@@ -54,8 +56,10 @@ int xb_set_bit(struct xb *xb, unsigned long bit)
return 0;
}
bitmap = this_cpu_xchg(ida_bitmap, NULL);
- if (!bitmap)
+ if (!bitmap) {
+ __radix_tree_delete(root, node, slot);
return -EAGAIN;
+ }
memset(bitmap, 0, sizeof(*bitmap));
__radix_tree_replace(root, node, slot, bitmap, NULL);
}
@@ -73,7 +77,7 @@ EXPORT_SYMBOL(xb_set_bit);
* This function is used to clear a bit in the xbitmap. If all the bits of the
* bitmap are 0, the bitmap will be freed.
*/
-int xb_clear_bit(struct xb *xb, unsigned long bit)
+void xb_clear_bit(struct xb *xb, unsigned long bit)
{
unsigned long index = bit / IDA_BITMAP_BITS;
struct radix_tree_root *root = &xb->xbrt;
@@ -90,25 +94,23 @@ int xb_clear_bit(struct xb *xb, unsigned long bit)
unsigned long tmp = (unsigned long)bitmap;
if (ebit >= BITS_PER_LONG)
- return 0;
+ return;
tmp &= ~(1UL << ebit);
if (tmp == RADIX_TREE_EXCEPTIONAL_ENTRY)
__radix_tree_delete(root, node, slot);
else
rcu_assign_pointer(*slot, (void *)tmp);
- return 0;
+ return;
}
if (!bitmap)
- return 0;
+ return;
__clear_bit(bit, bitmap->bitmap);
if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {
kfree(bitmap);
__radix_tree_delete(root, node, slot);
}
-
- return 0;
}
EXPORT_SYMBOL(xb_clear_bit);
@@ -133,7 +135,7 @@ bool xb_test_bit(const struct xb *xb, unsigned long bit)
return false;
if (radix_tree_exception(bitmap)) {
bit += RADIX_TREE_EXCEPTIONAL_SHIFT;
- if (bit > BITS_PER_LONG)
+ if (bit >= BITS_PER_LONG)
return false;
return (unsigned long)bitmap & (1UL << bit);
}
@@ -151,9 +153,9 @@ void xbitmap_check_bit(unsigned long bit)
assert(!xb_test_bit(&xb1, bit));
assert(xb_set_bit(&xb1, bit) == 0);
assert(xb_test_bit(&xb1, bit));
- assert(xb_clear_bit(&xb1, bit) == 0);
+ xb_clear_bit(&xb1, bit);
assert(xb_empty(&xb1));
- assert(xb_clear_bit(&xb1, bit) == 0);
+ xb_clear_bit(&xb1, bit);
assert(xb_empty(&xb1));
xb_preload_end();
}
--
2.7.4
next prev parent reply other threads:[~2017-11-29 14:11 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 13:55 [PATCH v18 00/10] Virtio-balloon Enhancement Wei Wang
2017-11-29 13:55 ` [PATCH v18 01/10] idr: add #include <linux/bug.h> Wei Wang
2017-11-30 0:58 ` Matthew Wilcox
2017-11-30 7:07 ` Michal Hocko
2017-11-30 21:49 ` Andrew Morton
2017-11-29 13:55 ` [PATCH v18 02/10] radix tree test suite: remove ARRAY_SIZE to avoid redefinition Wei Wang
2017-11-29 13:55 ` [PATCH v18 03/10] xbitmap: Introduce xbitmap Wei Wang
2017-11-29 13:55 ` Wei Wang [this message]
2017-11-29 13:55 ` [PATCH v18 05/10] xbitmap: add more operations Wei Wang
2017-11-30 10:34 ` Tetsuo Handa
2017-11-30 13:35 ` Tetsuo Handa
2017-11-30 14:39 ` Matthew Wilcox
2017-12-03 1:44 ` Tetsuo Handa
2017-12-01 8:02 ` Wei Wang
2017-12-01 13:02 ` Tetsuo Handa
2017-12-01 14:13 ` Matthew Wilcox
2017-12-01 15:09 ` Wang, Wei W
2017-12-01 17:25 ` Matthew Wilcox
2017-12-03 1:50 ` Tetsuo Handa
2017-12-07 12:01 ` Wei Wang
2017-12-07 15:41 ` Michael S. Tsirkin
2017-11-29 13:55 ` [PATCH v18 06/10] virtio_ring: add a new API, virtqueue_add_one_desc Wei Wang
2017-11-30 19:38 ` Michael S. Tsirkin
2017-12-01 8:06 ` Wei Wang
2017-11-29 13:55 ` [PATCH v18 07/10] virtio-balloon: VIRTIO_BALLOON_F_SG Wei Wang
2017-11-30 10:35 ` Tetsuo Handa
2017-11-30 16:25 ` Wang, Wei W
2017-12-01 15:38 ` Michael S. Tsirkin
2017-12-04 3:46 ` Wei Wang
2017-11-29 13:55 ` [PATCH v18 08/10] mm: support reporting free page blocks Wei Wang
2017-11-29 13:55 ` [PATCH v18 09/10] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ Wei Wang
2017-11-29 13:55 ` [PATCH v18 10/10] virtio-balloon: don't report free pages when page poisoning is enabled Wei Wang
2017-12-01 15:49 ` Michael S. Tsirkin
2017-12-04 5:39 ` Wei Wang
2017-12-11 6:38 ` Wei Wang
2017-12-11 13:24 ` Michael S. Tsirkin
2017-12-12 12:21 ` Wei Wang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1511963726-34070-5-git-send-email-wei.w.wang@intel.com \
--to=wei.w.wang@intel.com \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=amit.shah@redhat.com \
--cc=cornelia.huck@de.ibm.com \
--cc=david@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=liliang.opensource@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mawilcox@microsoft.com \
--cc=mgorman@techsingularity.net \
--cc=mhocko@kernel.org \
--cc=mst@redhat.com \
--cc=nilal@redhat.com \
--cc=pbonzini@redhat.com \
--cc=penguin-kernel@I-love.SAKURA.ne.jp \
--cc=qemu-devel@nongnu.org \
--cc=quan.xu@aliyun.com \
--cc=riel@redhat.com \
--cc=virtio-dev@lists.oasis-open.org \
--cc=virtualization@lists.linux-foundation.org \
--cc=willy@infradead.org \
--cc=yang.zhang.wz@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).