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Date: Thu, 23 Aug 2012 16:32:44 -0400
From: Ed Cashin <ecashin@...aid.com>
To: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/14] aoe: for performance support larger packet payloads
I probably should have Cc'ed the netdev list for this patch.
Ed Cashin <ecashin@...aid.com> writes:
> 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@...ira.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@...aid.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;
--
Ed
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