From: ming.lei-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org To: greg-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org, stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org Cc: linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Ming Lei <ming.lei-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> Subject: [PATCH] usb: ehci: fix update qtd->token in qh_append_tds Date: Sat, 27 Aug 2011 22:48:35 +0800 [thread overview] Message-ID: <1314456515-16419-1-git-send-email-ming.lei@canonical.com> (raw) From: Ming Lei <ming.lei-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> This patch fixs one performance bug on ARM Cortex A9 dual core platform, which has been reported on quite a few ARM machines(OMAP4, Tegra 2, snowball...), see details from link of https://bugs.launchpad.net/bugs/709245. In fact, one mb() on ARM is enough to flush L2 cache, but 'dummy->hw_token = token;' after mb() is added just for obeying correct mb() usage. The patch has been tested ok on OMAP4 panda A1 board, the performance of 'dd' over usb mass storage can be increased from 4~5MB/sec to 14~16MB/sec after applying this patch. Signed-off-by: Ming Lei <ming.lei-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> --- drivers/usb/host/ehci-q.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-) diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c index 0917e3a..65b5021 100644 --- a/drivers/usb/host/ehci-q.c +++ b/drivers/usb/host/ehci-q.c @@ -1082,6 +1082,20 @@ static struct ehci_qh *qh_append_tds ( wmb (); dummy->hw_token = token; + /* The mb() below is added to make sure that + * 'token' can be writen into qtd, so that ehci + * HC can see the up-to-date qtd descriptor. On + * some archs(at least on ARM Cortex A9 dual core), + * writing into coherenet memory doesn't mean the + * value written can reach physical memory + * immediately, and the value may be buffered + * inside L2 cache. 'dummy->hw_token = token;' + * after mb() is added for obeying correct mb() + * usage. + * */ + mb(); + token = dummy->hw_token; + urb->hcpriv = qh_get (qh); } } -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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From: ming.lei@canonical.com (ming.lei at canonical.com) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH] usb: ehci: fix update qtd->token in qh_append_tds Date: Sat, 27 Aug 2011 22:48:35 +0800 [thread overview] Message-ID: <1314456515-16419-1-git-send-email-ming.lei@canonical.com> (raw) From: Ming Lei <ming.lei@canonical.com> This patch fixs one performance bug on ARM Cortex A9 dual core platform, which has been reported on quite a few ARM machines(OMAP4, Tegra 2, snowball...), see details from link of https://bugs.launchpad.net/bugs/709245. In fact, one mb() on ARM is enough to flush L2 cache, but 'dummy->hw_token = token;' after mb() is added just for obeying correct mb() usage. The patch has been tested ok on OMAP4 panda A1 board, the performance of 'dd' over usb mass storage can be increased from 4~5MB/sec to 14~16MB/sec after applying this patch. Signed-off-by: Ming Lei <ming.lei@canonical.com> --- drivers/usb/host/ehci-q.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-) diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c index 0917e3a..65b5021 100644 --- a/drivers/usb/host/ehci-q.c +++ b/drivers/usb/host/ehci-q.c @@ -1082,6 +1082,20 @@ static struct ehci_qh *qh_append_tds ( wmb (); dummy->hw_token = token; + /* The mb() below is added to make sure that + * 'token' can be writen into qtd, so that ehci + * HC can see the up-to-date qtd descriptor. On + * some archs(at least on ARM Cortex A9 dual core), + * writing into coherenet memory doesn't mean the + * value written can reach physical memory + * immediately, and the value may be buffered + * inside L2 cache. 'dummy->hw_token = token;' + * after mb() is added for obeying correct mb() + * usage. + * */ + mb(); + token = dummy->hw_token; + urb->hcpriv = qh_get (qh); } } -- 1.7.4.1
next reply other threads:[~2011-08-27 14:48 UTC|newest] Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-08-27 14:48 ming.lei-Z7WLFzj8eWMS+FvcfC7Uqw [this message] 2011-08-27 14:48 ` [PATCH] usb: ehci: fix update qtd->token in qh_append_tds ming.lei at canonical.com 2011-08-27 15:03 ` Santosh 2011-08-27 15:03 ` Santosh [not found] ` <4E590756.9030307-l0cyMroinI0@public.gmane.org> 2011-08-27 15:18 ` Ming Lei 2011-08-27 15:18 ` Ming Lei [not found] ` <CACVXFVPPPUsntdCT=m=vRJ9XVksn6rGMzqJVvdD+sj=eOcTadg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2011-08-27 15:46 ` Santosh 2011-08-27 15:46 ` Santosh [not found] ` <1314456515-16419-1-git-send-email-ming.lei-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> 2011-08-27 15:13 ` Greg KH 2011-08-27 15:13 ` Greg KH 2011-08-27 15:33 ` Ming Lei 2011-08-27 15:33 ` Ming Lei 2011-08-27 16:07 ` Greg KH 2011-08-27 16:07 ` Greg KH 2011-08-27 16:57 ` Ming Lei 2011-08-27 16:57 ` Ming Lei [not found] ` <CACVXFVNz_ic_PPM_vNn1Dz85A2z94kRFso4rcqrvJfuLSqRSCg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2011-08-27 17:20 ` Ming Lei 2011-08-27 17:20 ` Ming Lei 2011-08-27 20:11 ` Alan Stern 2011-08-27 20:11 ` Alan Stern 2011-08-28 3:35 ` Ming Lei 2011-08-28 3:35 ` Ming Lei 2011-08-27 20:06 ` Alan Stern 2011-08-27 20:06 ` Alan Stern 2011-08-28 3:13 ` Ming Lei 2011-08-28 3:13 ` Ming Lei [not found] ` <CACVXFVP8Lr=ggH4FjvMQd6r9poLAT1r+_S3Z-NimP0i08DsQ8g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2011-08-28 17:00 ` Alan Stern 2011-08-28 17:00 ` Alan Stern 2011-08-28 23:36 ` Russell King - ARM Linux 2011-08-28 23:36 ` Russell King - ARM Linux 2011-08-29 1:51 ` Alan Stern 2011-08-29 1:51 ` Alan Stern 2011-08-29 8:52 ` Russell King - ARM Linux 2011-08-29 8:52 ` Russell King - ARM Linux 2011-08-29 13:57 ` Alan Stern 2011-08-29 13:57 ` Alan Stern [not found] ` <Pine.LNX.4.44L0.1108290951250.2525-100000-IYeN2dnnYyZXsRXLowluHWD2FQJk+8+b@public.gmane.org> 2011-08-29 15:55 ` Ming Lei 2011-08-29 15:55 ` Ming Lei 2011-08-29 16:24 ` Mark Salter 2011-08-29 16:24 ` Mark Salter [not found] ` <Pine.LNX.4.44L0.1108281233270.3742-100000-pYrvlCTfrz9XsRXLowluHWD2FQJk+8+b@public.gmane.org> 2011-08-29 14:25 ` Ming Lei 2011-08-29 14:25 ` Ming Lei [not found] ` <CACVXFVOvw6bSfcOYR2RWJO=k1WLgSCUygmSwZmtRDdM_tZNWEA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2011-08-29 15:03 ` Alan Stern 2011-08-29 15:03 ` Alan Stern [not found] ` <Pine.LNX.4.44L0.1108291046540.2525-100000-IYeN2dnnYyZXsRXLowluHWD2FQJk+8+b@public.gmane.org> 2011-08-29 15:21 ` Ming Lei 2011-08-29 15:21 ` Ming Lei 2011-08-29 16:33 ` Alan Stern 2011-08-29 16:33 ` Alan Stern [not found] ` <Pine.LNX.4.44L0.1108291218040.2525-100000-IYeN2dnnYyZXsRXLowluHWD2FQJk+8+b@public.gmane.org> 2011-08-30 14:02 ` Ming Lei 2011-08-30 14:02 ` Ming Lei 2011-08-27 16:31 ` Sergei Shtylyov 2011-08-27 16:31 ` Sergei Shtylyov -- strict thread matches above, loose matches on Subject: below -- 2011-08-27 14:46 ming.lei-Z7WLFzj8eWMS+FvcfC7Uqw
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