| Message ID | 20230428104124.1044-4-alejandro.vallejo@cloud.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Rationalize usage of xc_domain_getinfo{,list}() | expand |
On 28/04/2023 11:41 am, Alejandro Vallejo wrote: > It has 2 avoidable occurences > > * Check whether a domain is valid, which can be done faster with > xc_domain_getinfo_single() > * Domain discovery, which can be done much faster with the sysctl > interface through xc_domain_getinfolist(). It occurs to me that this isn't really right here. It's true in principle, but switching to requesting all domains at once is a fix for a race condition. I'd suggest "which can be done in a race free way through ..." and avoid saying faster. It's likely not faster now with the 4M bounce, but we can fix that in due course.
On 28/04/2023 1:33 pm, Andrew Cooper wrote: > On 28/04/2023 11:41 am, Alejandro Vallejo wrote: >> It has 2 avoidable occurences >> >> * Check whether a domain is valid, which can be done faster with >> xc_domain_getinfo_single() >> * Domain discovery, which can be done much faster with the sysctl >> interface through xc_domain_getinfolist(). > It occurs to me that this isn't really right here. > > It's true in principle, but switching to requesting all domains at once > is a fix for a race condition. > > I'd suggest "which can be done in a race free way through ..." and avoid > saying faster. It's likely not faster now with the 4M bounce, but we > can fix that in due course. Oh, there's also one tabs/spaces indentation hiccup. That can be fixed on commit too. ~Andrew
On Fri, Apr 28, 2023 at 01:33:45PM +0100, Andrew Cooper wrote: > On 28/04/2023 11:41 am, Alejandro Vallejo wrote: > > It has 2 avoidable occurences > > > > * Check whether a domain is valid, which can be done faster with > > xc_domain_getinfo_single() > > * Domain discovery, which can be done much faster with the sysctl > > interface through xc_domain_getinfolist(). > > It occurs to me that this isn't really right here. > > It's true in principle, but switching to requesting all domains at once > is a fix for a race condition. > > I'd suggest "which can be done in a race free way through ..." and avoid > saying faster. It's likely not faster now with the 4M bounce, but we > can fix that in due course. I agree, yes. Alejandro
diff --git a/tools/console/daemon/io.c b/tools/console/daemon/io.c index 6bfe96715b..c5972cb721 100644 --- a/tools/console/daemon/io.c +++ b/tools/console/daemon/io.c @@ -405,13 +405,7 @@ static void buffer_advance(struct buffer *buffer, size_t len) static bool domain_is_valid(int domid) { - bool ret; - xc_dominfo_t info; - - ret = (xc_domain_getinfo(xc, domid, 1, &info) == 1 && - info.domid == domid); - - return ret; + return xc_domain_getinfo_single(xc, domid, NULL) == 0; } static int create_hv_log(void) @@ -961,24 +955,33 @@ static unsigned enum_pass = 0; static void enum_domains(void) { - int domid = 1; - xc_dominfo_t dominfo; + /** + * Memory set aside to query the state of every + * domain in the hypervisor in a single hypercall. + */ + static xc_domaininfo_t domaininfo[DOMID_FIRST_RESERVED - 1]; + + int ret; struct domain *dom; enum_pass++; - while (xc_domain_getinfo(xc, domid, 1, &dominfo) == 1) { - dom = lookup_domain(dominfo.domid); - if (dominfo.dying) { + /* Fetch info on every valid domain except for dom0 */ + ret = xc_domain_getinfolist(xc, 1, DOMID_FIRST_RESERVED - 1, domaininfo); + if (ret < 0) + return; + + for (size_t i = 0; i < ret; i++) { + dom = lookup_domain(domaininfo[i].domain); + if (domaininfo[i].flags & XEN_DOMINF_dying) { if (dom) shutdown_domain(dom); } else { if (dom == NULL) - dom = create_domain(dominfo.domid); + dom = create_domain(domaininfo[i].domain); } if (dom) dom->last_seen = enum_pass; - domid = dominfo.domid + 1; } }
It has 2 avoidable occurences * Check whether a domain is valid, which can be done faster with xc_domain_getinfo_single() * Domain discovery, which can be done much faster with the sysctl interface through xc_domain_getinfolist(). Signed-off-by: Alejandro Vallejo <alejandro.vallejo@cloud.com> --- Cc: Andrew Cooper <andrew.cooper3@citrix.com> Cc: Wei Liu <wl@xen.org> Cc: Anthony PERARD <anthony.perard@citrix.com> --- tools/console/daemon/io.c | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-)