From patchwork Sat Aug 7 09:47:13 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marko Ristola X-Patchwork-Id: 118147 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter.kernel.org (8.14.4/8.14.3) with ESMTP id o779lQiP024546 for ; Sat, 7 Aug 2010 09:47:26 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753243Ab0HGJrX (ORCPT ); Sat, 7 Aug 2010 05:47:23 -0400 Received: from emh06.mail.saunalahti.fi ([62.142.5.116]:36140 "EHLO emh06.mail.saunalahti.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753163Ab0HGJrV (ORCPT ); Sat, 7 Aug 2010 05:47:21 -0400 Received: from saunalahti-vams (vs3-11.mail.saunalahti.fi [62.142.5.95]) by emh06-2.mail.saunalahti.fi (Postfix) with SMTP id E7EBFC79B5 for ; Sat, 7 Aug 2010 12:47:19 +0300 (EEST) Received: from emh02.mail.saunalahti.fi ([62.142.5.108]) by vs3-11.mail.saunalahti.fi ([62.142.5.95]) with SMTP (gateway) id A079BCE4608; Sat, 07 Aug 2010 12:47:19 +0300 Received: from tammi.koti (a88-114-153-83.elisa-laajakaista.fi [88.114.153.83]) by emh02.mail.saunalahti.fi (Postfix) with ESMTP id CE13E2BD45 for ; Sat, 7 Aug 2010 12:47:18 +0300 (EEST) Message-ID: <4C5D2BA1.60804@kolumbus.fi> Date: Sat, 07 Aug 2010 12:47:13 +0300 From: Marko Ristola User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.7) Gecko/20100720 Fedora/3.1.1-1.fc13 Thunderbird/3.1.1 MIME-Version: 1.0 To: Linux Media Mailing List Subject: Re: [PATCH] Avoid unnecessary data copying inside dvb_dmx_swfilter_204() function X-Antivirus: VAMS Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.3 (demeter.kernel.org [140.211.167.41]); Sat, 07 Aug 2010 09:47:30 +0000 (UTC) diff --git a/drivers/media/dvb/dvb-core/dvb_demux.c b/drivers/media/dvb/dvb-core/dvb_demux.c index 977ddba..b71d77d 100644 --- a/drivers/media/dvb/dvb-core/dvb_demux.c +++ b/drivers/media/dvb/dvb-core/dvb_demux.c @@ -478,97 +478,96 @@ void dvb_dmx_swfilter_packets(struct dvb_demux *demux, const u8 *buf, EXPORT_SYMBOL(dvb_dmx_swfilter_packets); -void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count) +static inline int findNextPacket(const u8 *buf, int pos, size_t count, + const int pktsize) { - int p = 0, i, j; + int start = pos, lost; - spin_lock(&demux->lock); - - if (demux->tsbufp) { - i = demux->tsbufp; - j = 188 - i; - if (count < j) { - memcpy(&demux->tsbuf[i], buf, count); - demux->tsbufp += count; - goto bailout; - } - memcpy(&demux->tsbuf[i], buf, j); - if (demux->tsbuf[0] == 0x47) - dvb_dmx_swfilter_packet(demux, demux->tsbuf); - demux->tsbufp = 0; - p += j; + while(likely(pos < count)) { + if (likely(buf[pos] == 0x47 || + (pktsize == 204 && buf[pos] == 0xB8))) + break; + pos++; } - while (p < count) { - if (buf[p] == 0x47) { - if (count - p >= 188) { - dvb_dmx_swfilter_packet(demux, &buf[p]); - p += 188; - } else { - i = count - p; - memcpy(demux->tsbuf, &buf[p], i); - demux->tsbufp = i; - goto bailout; - } - } else - p++; + if (unlikely(lost = pos - start)) { + /* This garbage is part of a valid packet? */ + int backtrack = pos - pktsize; + if (backtrack >= 0 && (buf[backtrack] == 0x47 || + (pktsize == 204 && buf[backtrack] == 0xB8))) { + /* printk("demux: backtracked %d bytes" + * "\n", start - backtrack); */ + return backtrack; + } + /*printk("demux: skipped %d bytes at %d\n", lost, start); */ } -bailout: - spin_unlock(&demux->lock); + return pos; } -EXPORT_SYMBOL(dvb_dmx_swfilter); - -void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf, size_t count) +/* Filter all pktsize= 188 or 204 sized packets and skip garbage. */ +static inline void _dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, + size_t count, const int pktsize) { int p = 0, i, j; - u8 tmppack[188]; + const u8 *q; spin_lock(&demux->lock); - if (demux->tsbufp) { + if (likely(demux->tsbufp)) { /* tsbuf[0] is now 0x47. */ i = demux->tsbufp; - j = 204 - i; - if (count < j) { + j = pktsize - i; + if (unlikely(count < j)) { memcpy(&demux->tsbuf[i], buf, count); demux->tsbufp += count; goto bailout; } memcpy(&demux->tsbuf[i], buf, j); - if ((demux->tsbuf[0] == 0x47) || (demux->tsbuf[0] == 0xB8)) { - memcpy(tmppack, demux->tsbuf, 188); - if (tmppack[0] == 0xB8) - tmppack[0] = 0x47; - dvb_dmx_swfilter_packet(demux, tmppack); - } + if (likely(demux->tsbuf[0] == 0x47)) /* double check */ + dvb_dmx_swfilter_packet(demux, demux->tsbuf); demux->tsbufp = 0; p += j; } - while (p < count) { - if ((buf[p] == 0x47) || (buf[p] == 0xB8)) { - if (count - p >= 204) { - memcpy(tmppack, &buf[p], 188); - if (tmppack[0] == 0xB8) - tmppack[0] = 0x47; - dvb_dmx_swfilter_packet(demux, tmppack); - p += 204; - } else { - i = count - p; - memcpy(demux->tsbuf, &buf[p], i); - demux->tsbufp = i; - goto bailout; - } - } else { - p++; + while (likely((p = findNextPacket(buf, p, count, pktsize)) < count)) { + if (unlikely(count - p < pktsize)) + break; + + q = &buf[p]; + + if (unlikely(pktsize == 204 && (*q == 0xB8))) { + memcpy(demux->tsbuf, q, 188); + demux->tsbuf[0] = 0x47; + q = demux->tsbuf; } + dvb_dmx_swfilter_packet(demux, q); + p += pktsize; + } + + i = count - p; + if (likely(i)) { + memcpy(demux->tsbuf, &buf[p], i); + demux->tsbufp = i; + if (unlikely(pktsize == 204 && demux->tsbuf[0] == 0xB8)) + demux->tsbuf[0] = 0x47; } bailout: spin_unlock(&demux->lock); } +void dvb_dmx_swfilter(struct dvb_demux *demux, const u8 *buf, size_t count) +{ + _dvb_dmx_swfilter(demux, buf, count, 188); +} + +EXPORT_SYMBOL(dvb_dmx_swfilter); + +void dvb_dmx_swfilter_204(struct dvb_demux *demux, const u8 *buf, size_t count) +{ + _dvb_dmx_swfilter(demux, buf, count, 204); +} + EXPORT_SYMBOL(dvb_dmx_swfilter_204); static struct dvb_demux_filter *dvb_dmx_filter_alloc(struct dvb_demux *demux)