Date: Thu, 22 Sep 2016 12:40:50 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Julien Charbon <jch@freebsd.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, freebsd-stable@FreeBSD.org, hiren panchasara <hiren@strugglingcoder.info> Subject: Re: 11.0 stuck on high network load Message-ID: <20160922094050.GA2840@zxy.spb.ru> In-Reply-To: <05ba1a3a-2d99-f8e2-40a1-4c1fca317db3@freebsd.org> References: <20160916181839.GC2960@zxy.spb.ru> <20160916183053.GL9397@strugglingcoder.info> <20160916190330.GG2840@zxy.spb.ru> <78cbcdc9-f565-1046-c157-2ddd8fcccc62@freebsd.org> <20160919204328.GN2840@zxy.spb.ru> <8ba75d6e-4f01-895e-0aed-53c6c6692cb9@freebsd.org> <20160920202633.GQ2840@zxy.spb.ru> <f644cd52-4377-aa90-123a-3a2887972bbc@freebsd.org> <20160921083148.GU2840@zxy.spb.ru> <05ba1a3a-2d99-f8e2-40a1-4c1fca317db3@freebsd.org>
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On Thu, Sep 22, 2016 at 11:28:38AM +0200, Julien Charbon wrote: > >>> What purpose to not skip locked tcptw in this loop? > >> > >> If I understand your question correctly: According to your pmcstat > >> result, tcp_tw_2msl_scan() currently struggles with a write lock > >> (__rw_wlock_hard) and the only write lock used tcp_tw_2msl_scan() is > >> INP_WLOCK. No sign of contention on TW_RLOCK(V_tw_lock) currently. > > > > As I see in code, tcp_tw_2msl_scan got first node from V_twq_2msl and > > need got RW lock on inp w/o alternates. Can tcp_tw_2msl_scan skip current node > > and go to next node in V_twq_2msl list if current node locked by some > > reasson? > > Interesting question indeed: It is not optimal that all simultaneous > calls to tcp_tw_2msl_scan() compete for the same oldest tcptw. The next > tcptws in the list are certainly old enough also. > > Let me see if I can make a simple change that makes kernel threads > calling tcp_tw_2msl_scan() at same time to work on a different old > enough tcptws. So far, I found only solutions quite complex to implement. Simple solution is skip in each thread ncpu elemnts and skip curent cpu number elements at start, if I understund you correctly.
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