From mboxrd@z Thu Jan 1 00:00:00 1970 From: Don Slutz Subject: Re: [PATCH v4 03/15] xenctx: Add -m (--multiple_pages) option to output larger stack Date: Wed, 19 Mar 2014 21:19:50 -0400 Message-ID: <532A4236.8060704@terremark.com> References: <1395180940-23901-1-git-send-email-dslutz@verizon.com> <1395180940-23901-4-git-send-email-dslutz@verizon.com> <5329B8EF.2080000@eu.citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5329B8EF.2080000@eu.citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: George Dunlap Cc: Ian Campbell , Stefano Stabellini , Don Slutz , Ian Jackson , Don Slutz , xen-devel@lists.xen.org, Jan Beulich List-Id: xen-devel@lists.xenproject.org On 03/19/14 11:34, George Dunlap wrote: > On 03/18/2014 10:15 PM, Don Slutz wrote: >> From: Don Slutz >> >> Important: This is the stack size to display not the configured >> stack size. >> >> Using pictures (for a 3 page configured system): >> >> +------------------+ >> | | >> | | >> | | >> | | >> | | >> +------------------+ >> | | >> | | >> | | >> | | >> | | >> +------------------+ >> | | >> | | >> | | >> SP --> | | >> | | >> +------------------+ > > Sorry, what is this a picture of? I can't make any sense out of it. > Shouldn't this have only one box, the next have two, and the bottom > one have three? > This is various pictures of a 3 page stack, and where the SP currently is. Each box is a page. So here the "stack limit" is the end of 1 page. In the sense of how much stack is used, you are right it is 1, 2 and then 3. This tracks with the value passed for "-m" (see next line). >> >> Display using "-m 1" since the used stack pages is 1. >> >> +------------------+ >> | | >> | | >> | | >> | | >> | | >> +------------------+ >> | | >> SP --> | | >> | | >> | | >> | | >> +------------------+ >> | | >> | | >> | | >> | | >> | | >> +------------------+ >> Here the stack limit is end of page + 1 full page. >> Display using "-m 2" since the used stack pages is 2. >> >> +------------------+ >> | | >> | | >> | | >> | | >> SP --> | | >> +------------------+ >> | | >> | | >> | | >> | | >> | | >> +------------------+ >> | | >> | | >> | | >> | | >> | | >> +------------------+ >> >> Display using "-m 3" since the used stack pages is 3. >> Here the stack limit is end of page + 2 full pages. >> Signed-off-by: Don Slutz >> --- >> v4 Converted from xenctx: Add -2 (--two-pages) option to switch stack >> size to 8KiB >> >> tools/xentrace/xenctx.c | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/tools/xentrace/xenctx.c b/tools/xentrace/xenctx.c >> index 42a47f3..6da38cc 100644 >> --- a/tools/xentrace/xenctx.c >> +++ b/tools/xentrace/xenctx.c >> @@ -35,6 +35,7 @@ static struct xenctx { >> int frame_ptrs; >> int stack_trace; >> int disp_all; >> + int multiple_pages; >> int all_vcpus; >> int self_paused; >> xc_dominfo_t dominfo; >> @@ -664,6 +665,8 @@ static int print_stack(vcpu_guest_context_any_t >> *ctx, int vcpu, int width) >> stack_limit = ((stack_pointer(ctx) + XC_PAGE_SIZE) >> & ~((guest_word_t) XC_PAGE_SIZE - 1)); >> + if ( xenctx.multiple_pages > 1 ) >> + stack_limit += (xenctx.multiple_pages - 1) * XC_PAGE_SIZE; >> printf("\n"); >> printf("Stack:\n"); >> for (i=1; i<5 && stack < stack_limit; i++) { >> @@ -834,18 +837,21 @@ static void usage(void) >> kernel_start); >> printf(" -a, --all display more registers\n"); >> printf(" -C, --all-vcpus print info for all vcpus\n"); >> + printf(" -m PAGES, --multiple-pages=PAGES\n"); >> + printf(" assume the kernel was compiled with >> PAGES (default 1) of stacks.\n"); >> } Opps, this needs fixing. >> int main(int argc, char **argv) >> { >> int ch; >> int ret; >> - static const char *sopts = "fs:hak:SC"; >> + static const char *sopts = "fs:hak:SCm:"; >> static const struct option lopts[] = { >> {"stack-trace", 0, NULL, 'S'}, >> {"symbol-table", 1, NULL, 's'}, >> {"frame-pointers", 0, NULL, 'f'}, >> {"kernel-start", 1, NULL, 'k'}, >> + {"multiple-pages", 0, NULL, 'm'}, > > I think I would call the long option "kernel-stack-pages" or something > like that. "Multiple pages" doesn't really convey much meaning. -m > is probably a fine short option, but -n might be more memorable. > The issue with "kernel-stack-pages" is that it leads to configured kernel stack pages (which for the pictures above is 3). 3 is most likely not the number to use here. A big part of this is that how a "kernel" knows where it is in the stack can be simple like for a 2 page stack, 1 page is odd, 2nd page is even. (3 pages is most likely more complex, but fence page(s) may help here.) Maybe stack-limit-in-pages is better? -Don Slutz > -George >