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Subject[PATCH 01/14] aoe: for performance support larger packet payloads
This patch adds the ability to work with large packets composed of a
number of segments, using the scatter gather feature of the block
layer (biovecs) and the network layer (skb frag array). The
motivation is the performance gained by using a packet data payload
greater than a page size and by using the network card's scatter
gather feature.

Users of the out-of-tree aoe driver already had these changes, but
since early 2011, they have complained of increased memory utilization
and higher CPU utilization during heavy writes.[1] The commit below
appears related, as it disables scatter gather on non-IP protocols
inside the harmonize_features function, even when the NIC supports sg.

commit f01a5236bd4b140198fbcc550f085e8361fd73fa
Author: Jesse Gross <jesse@nicira.com>
Date: Sun Jan 9 06:23:31 2011 +0000

net offloading: Generalize netif_get_vlan_features().

With that regression in place, transmits always linearize sg AoE
packets, but in-kernel users did not have this patch. Before 2.6.38,
though, these changes were working to allow sg to increase
performance.

1. http://www.spinics.net/lists/linux-mm/msg15184.html

Signed-off-by: Ed Cashin <ecashin@coraid.com>
---
drivers/block/aoe/aoe.h | 2 +
drivers/block/aoe/aoeblk.c | 3 +
drivers/block/aoe/aoecmd.c | 138 ++++++++++++++++++++++++++++++-------------
drivers/block/aoe/aoedev.c | 1 +
drivers/block/aoe/aoenet.c | 13 +++-
5 files changed, 111 insertions(+), 46 deletions(-)

diff --git a/drivers/block/aoe/aoe.h b/drivers/block/aoe/aoe.h
index db195ab..8ca8c8a 100644
--- a/drivers/block/aoe/aoe.h
+++ b/drivers/block/aoe/aoe.h
@@ -119,6 +119,8 @@ struct frame {
ulong bcnt;
sector_t lba;
struct sk_buff *skb;
+ struct bio_vec *bv;
+ ulong bv_off;
};

struct aoeif {
diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
index 321de7b..1471f81 100644
--- a/drivers/block/aoe/aoeblk.c
+++ b/drivers/block/aoe/aoeblk.c
@@ -279,6 +279,9 @@ aoeblk_gdalloc(void *vp)
if (bdi_init(&d->blkq->backing_dev_info))
goto err_blkq;
spin_lock_irqsave(&d->lock, flags);
+ blk_queue_max_hw_sectors(d->blkq, BLK_DEF_MAX_SECTORS);
+ d->blkq->backing_dev_info.ra_pages = BLK_DEF_MAX_SECTORS * 1024;
+ d->blkq->backing_dev_info.ra_pages /= PAGE_CACHE_SIZE;
gd->major = AOE_MAJOR;
gd->first_minor = d->sysminor * AOE_PARTITIONS;
gd->fops = &aoe_bdops;
diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index de0435e..f10ab49 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -164,7 +164,8 @@ freeframe(struct aoedev *d)
rf = f;
continue;
}
-gotone: skb_shinfo(skb)->nr_frags = skb->data_len = 0;
+gotone: skb->truesize -= skb->data_len;
+ skb_shinfo(skb)->nr_frags = skb->data_len = 0;
skb_trim(skb, 0);
d->tgt = t;
ifrotate(*t);
@@ -200,6 +201,24 @@ gotone: skb_shinfo(skb)->nr_frags = skb->data_len = 0;
return NULL;
}

+static void
+skb_fillup(struct sk_buff *skb, struct bio_vec *bv, ulong off, ulong cnt)
+{
+ int frag = 0;
+ ulong fcnt;
+loop:
+ fcnt = bv->bv_len - (off - bv->bv_offset);
+ if (fcnt > cnt)
+ fcnt = cnt;
+ skb_fill_page_desc(skb, frag++, bv->bv_page, off, fcnt);
+ cnt -= fcnt;
+ if (cnt <= 0)
+ return;
+ bv++;
+ off = bv->bv_offset;
+ goto loop;
+}
+
static int
aoecmd_ata_rw(struct aoedev *d)
{
@@ -210,7 +229,7 @@ aoecmd_ata_rw(struct aoedev *d)
struct bio_vec *bv;
struct aoetgt *t;
struct sk_buff *skb;
- ulong bcnt;
+ ulong bcnt, fbcnt;
char writebit, extbit;

writebit = 0x10;
@@ -225,8 +244,28 @@ aoecmd_ata_rw(struct aoedev *d)
bcnt = t->ifp->maxbcnt;
if (bcnt == 0)
bcnt = DEFAULTBCNT;
- if (bcnt > buf->bv_resid)
- bcnt = buf->bv_resid;
+ if (bcnt > buf->resid)
+ bcnt = buf->resid;
+ fbcnt = bcnt;
+ f->bv = buf->bv;
+ f->bv_off = f->bv->bv_offset + (f->bv->bv_len - buf->bv_resid);
+ do {
+ if (fbcnt < buf->bv_resid) {
+ buf->bv_resid -= fbcnt;
+ buf->resid -= fbcnt;
+ break;
+ }
+ fbcnt -= buf->bv_resid;
+ buf->resid -= buf->bv_resid;
+ if (buf->resid == 0) {
+ d->inprocess = NULL;
+ break;
+ }
+ buf->bv++;
+ buf->bv_resid = buf->bv->bv_len;
+ WARN_ON(buf->bv_resid == 0);
+ } while (fbcnt);
+
/* initialize the headers & frame */
skb = f->skb;
h = (struct aoe_hdr *) skb_mac_header(skb);
@@ -237,7 +276,6 @@ aoecmd_ata_rw(struct aoedev *d)
t->nout++;
f->waited = 0;
f->buf = buf;
- f->bufaddr = page_address(bv->bv_page) + buf->bv_off;
f->bcnt = bcnt;
f->lba = buf->sector;

@@ -252,10 +290,11 @@ aoecmd_ata_rw(struct aoedev *d)
ah->lba3 |= 0xe0; /* LBA bit + obsolete 0xa0 */
}
if (bio_data_dir(buf->bio) == WRITE) {
- skb_fill_page_desc(skb, 0, bv->bv_page, buf->bv_off, bcnt);
+ skb_fillup(skb, f->bv, f->bv_off, bcnt);
ah->aflags |= AOEAFL_WRITE;
skb->len += bcnt;
skb->data_len = bcnt;
+ skb->truesize += bcnt;
t->wpkts++;
} else {
t->rpkts++;
@@ -266,18 +305,7 @@ aoecmd_ata_rw(struct aoedev *d)

/* mark all tracking fields and load out */
buf->nframesout += 1;
- buf->bv_off += bcnt;
- buf->bv_resid -= bcnt;
- buf->resid -= bcnt;
buf->sector += bcnt >> 9;
- if (buf->resid == 0) {
- d->inprocess = NULL;
- } else if (buf->bv_resid == 0) {
- buf->bv = ++bv;
- buf->bv_resid = bv->bv_len;
- WARN_ON(buf->bv_resid == 0);
- buf->bv_off = bv->bv_offset;
- }

skb->dev = t->ifp->nd;
skb = skb_clone(skb, GFP_ATOMIC);
@@ -364,14 +392,12 @@ resend(struct aoedev *d, struct aoetgt *t, struct frame *f)
put_lba(ah, f->lba);

n = f->bcnt;
- if (n > DEFAULTBCNT)
- n = DEFAULTBCNT;
ah->scnt = n >> 9;
if (ah->aflags & AOEAFL_WRITE) {
- skb_fill_page_desc(skb, 0, virt_to_page(f->bufaddr),
- offset_in_page(f->bufaddr), n);
+ skb_fillup(skb, f->bv, f->bv_off, n);
skb->len = sizeof *h + sizeof *ah + n;
skb->data_len = n;
+ skb->truesize += n;
}
}
skb->dev = t->ifp->nd;
@@ -530,20 +556,6 @@ rexmit_timer(ulong vp)
ejectif(t, ifp);
ifp = NULL;
}
-
- if (ata_scnt(skb_mac_header(f->skb)) > DEFAULTBCNT / 512
- && ifp && ++ifp->lostjumbo > (t->nframes << 1)
- && ifp->maxbcnt != DEFAULTBCNT) {
- printk(KERN_INFO
- "aoe: e%ld.%d: "
- "too many lost jumbo on "
- "%s:%pm - "
- "falling back to %d frames.\n",
- d->aoemajor, d->aoeminor,
- ifp->nd->name, t->addr,
- DEFAULTBCNT);
- ifp->maxbcnt = 0;
- }
resend(d, t, f);
}

@@ -736,6 +748,45 @@ diskstats(struct gendisk *disk, struct bio *bio, ulong duration, sector_t sector
part_stat_unlock();
}

+static void
+bvcpy(struct bio_vec *bv, ulong off, struct sk_buff *skb, ulong cnt)
+{
+ ulong fcnt;
+ char *p;
+ int soff = 0;
+loop:
+ fcnt = bv->bv_len - (off - bv->bv_offset);
+ if (fcnt > cnt)
+ fcnt = cnt;
+ p = page_address(bv->bv_page) + off;
+ skb_copy_bits(skb, soff, p, fcnt);
+ soff += fcnt;
+ cnt -= fcnt;
+ if (cnt <= 0)
+ return;
+ bv++;
+ off = bv->bv_offset;
+ goto loop;
+}
+
+static void
+fadvance(struct frame *f, ulong cnt)
+{
+ ulong fcnt;
+
+ f->lba += cnt >> 9;
+loop:
+ fcnt = f->bv->bv_len - (f->bv_off - f->bv->bv_offset);
+ if (fcnt > cnt) {
+ f->bv_off += cnt;
+ return;
+ }
+ cnt -= fcnt;
+ f->bv++;
+ f->bv_off = f->bv->bv_offset;
+ goto loop;
+}
+
void
aoecmd_ata_rsp(struct sk_buff *skb)
{
@@ -753,6 +804,7 @@ aoecmd_ata_rsp(struct sk_buff *skb)
u16 aoemajor;

hin = (struct aoe_hdr *) skb_mac_header(skb);
+ skb_pull(skb, sizeof(*hin));
aoemajor = get_unaligned_be16(&hin->major);
d = aoedev_by_aoeaddr(aoemajor, hin->minor);
if (d == NULL) {
@@ -790,7 +842,8 @@ aoecmd_ata_rsp(struct sk_buff *skb)

calc_rttavg(d, tsince(f->tag));

- ahin = (struct aoe_atahdr *) (hin+1);
+ ahin = (struct aoe_atahdr *) skb->data;
+ skb_pull(skb, sizeof(*ahin));
hout = (struct aoe_hdr *) skb_mac_header(f->skb);
ahout = (struct aoe_atahdr *) (hout+1);
buf = f->buf;
@@ -809,7 +862,7 @@ aoecmd_ata_rsp(struct sk_buff *skb)
switch (ahout->cmdstat) {
case ATA_CMD_PIO_READ:
case ATA_CMD_PIO_READ_EXT:
- if (skb->len - sizeof *hin - sizeof *ahin < n) {
+ if (skb->len < n) {
printk(KERN_ERR
"aoe: %s. skb->len=%d need=%ld\n",
"runt data size in read", skb->len, n);
@@ -817,7 +870,7 @@ aoecmd_ata_rsp(struct sk_buff *skb)
spin_unlock_irqrestore(&d->lock, flags);
return;
}
- memcpy(f->bufaddr, ahin+1, n);
+ bvcpy(f->bv, f->bv_off, skb, n);
case ATA_CMD_PIO_WRITE:
case ATA_CMD_PIO_WRITE_EXT:
ifp = getif(t, skb->dev);
@@ -827,21 +880,22 @@ aoecmd_ata_rsp(struct sk_buff *skb)
ifp->lostjumbo = 0;
}
if (f->bcnt -= n) {
- f->lba += n >> 9;
- f->bufaddr += n;
+ fadvance(f, n);
resend(d, t, f);
goto xmit;
}
break;
case ATA_CMD_ID_ATA:
- if (skb->len - sizeof *hin - sizeof *ahin < 512) {
+ if (skb->len < 512) {
printk(KERN_INFO
"aoe: runt data size in ataid. skb->len=%d\n",
skb->len);
spin_unlock_irqrestore(&d->lock, flags);
return;
}
- ataid_complete(d, t, (char *) (ahin+1));
+ if (skb_linearize(skb))
+ break;
+ ataid_complete(d, t, skb->data);
break;
default:
printk(KERN_INFO
diff --git a/drivers/block/aoe/aoedev.c b/drivers/block/aoe/aoedev.c
index 6b5110a..b2d1fd3 100644
--- a/drivers/block/aoe/aoedev.c
+++ b/drivers/block/aoe/aoedev.c
@@ -182,6 +182,7 @@ skbfree(struct sk_buff *skb)
"cannot free skb -- memory leaked.");
return;
}
+ skb->truesize -= skb->data_len;
skb_shinfo(skb)->nr_frags = skb->data_len = 0;
skb_trim(skb, 0);
dev_kfree_skb(skb);
diff --git a/drivers/block/aoe/aoenet.c b/drivers/block/aoe/aoenet.c
index 4d3bc0d..0787807 100644
--- a/drivers/block/aoe/aoenet.c
+++ b/drivers/block/aoe/aoenet.c
@@ -102,7 +102,9 @@ static int
aoenet_rcv(struct sk_buff *skb, struct net_device *ifp, struct packet_type *pt, struct net_device *orig_dev)
{
struct aoe_hdr *h;
+ struct aoe_atahdr *ah;
u32 n;
+ int sn;

if (dev_net(ifp) != &init_net)
goto exit;
@@ -110,13 +112,16 @@ aoenet_rcv(struct sk_buff *skb, struct net_device *ifp, struct packet_type *pt,
skb = skb_share_check(skb, GFP_ATOMIC);
if (skb == NULL)
return 0;
- if (skb_linearize(skb))
- goto exit;
if (!is_aoe_netif(ifp))
goto exit;
skb_push(skb, ETH_HLEN); /* (1) */
-
- h = (struct aoe_hdr *) skb_mac_header(skb);
+ sn = sizeof(*h) + sizeof(*ah);
+ if (skb->len >= sn) {
+ sn -= skb_headlen(skb);
+ if (sn > 0 && !__pskb_pull_tail(skb, sn))
+ goto exit;
+ }
+ h = (struct aoe_hdr *) skb->data;
n = get_unaligned_be32(&h->tag);
if ((h->verfl & AOEFL_RSP) == 0 || (n & 1<<31))
goto exit;
--
1.7.2.5


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