Date: Wed, 12 May 2004 06:40:40 +0800 From: David Xu <davidxu@viatech.com.cn> To: David Xu <davidxu@viatech.com.cn> Cc: John Baldwin <jhb@freebsd.org> Subject: Re: Threads and userland profliing... Message-ID: <40A15668.1030103@viatech.com.cn> In-Reply-To: <40A15602.9020902@viatech.com.cn> References: <Pine.GSO.4.10.10405111755490.11212-100000@pcnet5.pcnet.com> <40A15602.9020902@viatech.com.cn>
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David Xu wrote: > Daniel Eischen wrote: > >> On Tue, 11 May 2004, John Baldwin wrote: >> >> >> >>> Currently in the pstats structure we have a uprof substructure that >>> holds various values used for userland processing. Does anyone know >>> what parts of that structure are supposed to be per-process and >>> which are supposed to be per-thread? pr_addr and pr_ticks seem to >>> be definite per-thread items, but the other values I'm not sure of. >>> >>> Specifically, is the userland table that pr_base, pr_size, pr_off, >>> and pr_scale refer to per-thread or is it supposed to be shared >>> among all threads in a process? If it's shared, do we need to be >>> using casuptr() or something similar in addupc_intr() instead of a >>> separate fetch and store? addupc_task() also has a race window >>> between the copyin() and copyout() as well if it is shared. If its >>> private, then I suppose each thread has to call profil(2) and gprof >>> is supposed to be smart enough to make that happen? Does POSIX have >>> anything to say regarding threads and profil(2)? >>> >> >> >> POSIX does not define profil(2). Here's what Solaris 9 has to >> say about it: >> >> In Solaris releases prior to 2.6, calling profil() in a mul- >> tithreaded program would impact only the calling LWP; the >> profile state was not inherited at LWP creation time. To >> profile a multithreaded program with a global profile >> buffer, each thread needed to issue a call to profil() at >> threads start-up time, and each thread had to be a bound >> thread. This was cumbersome and did not easily support >> dynamically turning profiling on and off. In Solaris 2.6, >> the profil() system call for multithreaded processes has >> global impact - that is, a call to profil() impacts all >> LWPs/threads in the process. This may cause applications >> that depend on the previous per-LWP semantic to break, but >> it is expected to improve multithreaded programs that wish >> to turn profiling on and off dynamically at runtime. >> >> We should probably avoid the mistake that Solaris < 2.6 >> made. >> >> >> > Because I never thought the profile buffer should be per-process, OOPS, I thought it should be per-process, not per-thread. > did you mean that it should be per-process too? > > David Xu > > > >
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