Date: Mon, 2 May 2011 22:55:55 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: arch@freebsd.org Subject: Re: [PATCH] Add ktrace records for user page faults Message-ID: <20110502195555.GC48734@deviant.kiev.zoral.com.ua> In-Reply-To: <201105021537.19507.jhb@freebsd.org> References: <201105021537.19507.jhb@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
[-- Attachment #1 --] On Mon, May 02, 2011 at 03:37:19PM -0400, John Baldwin wrote: > One thing I have found useful is knowing when processes are in the kernel > instead of in userland. ktrace already provides records for syscall > entry/exit. The other major source of time spent in the kernel that I've seen > is page fault handling. To that end, I have a patch that adds ktrace records > to the beginning and end of VM faults. This gives a pair of records so a user > can see how long a fault took (similar to how one can see how long a syscall > takes now). Sample output from kdump is below: > > 47565 echo CALL mmap(0x800a87000,0x179000,PROT_READ| > PROT_WRITE,MAP_PRIVATE|MAP_ANON,0xffffffff,0) > 47565 echo RET mmap 34370777088/0x800a87000 > 47565 echo PFLT 0x800723000 VM_PROT_EXECUTE > 47565 echo RET KERN_SUCCESS > 47565 echo CALL munmap(0x800887000,0x179000) > 47565 echo RET munmap 0 > 47565 echo PFLT 0x800a00000 VM_PROT_WRITE > 47565 echo RET KERN_SUCCESS > > The patch is available at www.freebsd.org/~jhb/patches/ktrace_fault.patch and > included below. One immediate detail is that trap() truncates the fault address to the page address, that arguably looses useful information. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iEYEARECAAYFAk2/DEsACgkQC3+MBN1Mb4jLCQCeOFcMzhtRL8/aHutAqSaKl2wz 7XUAn3O73HqERdXiKwFLqqC+yHJLl2// =Dcqf -----END PGP SIGNATURE-----
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20110502195555.GC48734>