Re: [dpdk-dev] [PATCH v3 3/7] service cores: coremask parsing

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Thu, 6 Jul 2017 14:47:20 +0000
> From: "Van Haaren, Harry" <harry.van.haaren@intel.com>
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> CC: "dev@dpdk.org" <dev@dpdk.org>, "thomas@monjalon.net"
>  <thomas@monjalon.net>, "Wiles, Keith" <keith.wiles@intel.com>,
>  "Richardson, Bruce" <bruce.richardson@intel.com>
> Subject: RE: [PATCH v3 3/7] service cores: coremask parsing
> 
> > From: Jerin Jacob [mailto:jerin.jacob@caviumnetworks.com]
> > Sent: Tuesday, July 4, 2017 1:46 PM
> > To: Van Haaren, Harry <harry.van.haaren@intel.com>
> > Cc: dev@dpdk.org; thomas@monjalon.net; Wiles, Keith <keith.wiles@intel.com>; Richardson,
> > Bruce <bruce.richardson@intel.com>
> > Subject: Re: [PATCH v3 3/7] service cores: coremask parsing
> > 
> > -----Original Message-----
> > > Date: Sun, 2 Jul 2017 22:35:10 +0100
> > > From: Harry van Haaren <harry.van.haaren@intel.com>
> > > To: dev@dpdk.org
> > > CC: jerin.jacob@caviumnetworks.com, thomas@monjalon.net,
> > >  keith.wiles@intel.com, bruce.richardson@intel.com, Harry van Haaren
> > >  <harry.van.haaren@intel.com>
> > > Subject: [PATCH v3 3/7] service cores: coremask parsing
> > > X-Mailer: git-send-email 2.7.4
> > >
> > > Add logic for parsing a coremask from EAL, which allows
> > > the application to be unaware of the cores being taken from
> > > its coremask.
> > >
> > > Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com>
> > >
> > > diff --git a/lib/librte_eal/common/eal_common_options.c
> > b/lib/librte_eal/common/eal_common_options.c
> > > index f470195..cee200c 100644
> > > --- a/lib/librte_eal/common/eal_common_options.c
> > > +++ b/lib/librte_eal/common/eal_common_options.c
> > > @@ -61,6 +61,7 @@ const char
> > >  eal_short_options[] =
> > >  	"b:" /* pci-blacklist */
> > >  	"c:" /* coremask */
> > > +	"s:" /* service coremask */
> > >  	"d:" /* driver */
> > >  	"h"  /* help */
> > >  	"l:" /* corelist */
> > > @@ -267,6 +268,73 @@ static int xdigit2val(unsigned char c)
> > >  }
> > 
> > Missing the --help update for service coremask details.
> > 
> > I think, EAL arguments are documented in another area of doc directory
> > as well. Update the documents.
> 
> Will double check / fix this. Replying here now to advance discussion below; 
> 
> > >  static int
> > > +eal_parse_service_coremask(const char *coremask)
> > > +{
> > > +	struct rte_config *cfg = rte_eal_get_configuration();
> > > +	int i, j, idx = 0;
> > > +	unsigned int count = 0;
> > > +	char c;
> > > +	int val;
> > > +
> > > +	if (coremask == NULL)
> > > +		return -1;
> > > +	/* Remove all blank characters ahead and after .
> > > +	 * Remove 0x/0X if exists.
> > > +	 */
> > > +	while (isblank(*coremask))
> > > +		coremask++;
> > > +	if (coremask[0] == '0' && ((coremask[1] == 'x')
> > > +		|| (coremask[1] == 'X')))
> > > +		coremask += 2;
> > > +	i = strlen(coremask);
> > > +	while ((i > 0) && isblank(coremask[i - 1]))
> > > +		i--;
> > > +
> > > +	if (i == 0)
> > > +		return -1;
> > > +
> > > +	for (i = i - 1; i >= 0 && idx < RTE_MAX_LCORE; i--) {
> > > +		c = coremask[i];
> > > +		if (isxdigit(c) == 0) {
> > > +			/* invalid characters */
> > > +			return -1;
> > > +		}
> > > +		val = xdigit2val(c);
> > > +		for (j = 0; j < BITS_PER_HEX && idx < RTE_MAX_LCORE;
> > > +				j++, idx++) {
> > > +			if ((1 << j) & val) {
> > > +				/* handle master lcore already parsed */
> > > +				uint32_t lcore = idx;
> > > +				if (master_lcore_parsed &&
> > > +						cfg->master_lcore == lcore)
> > > +					continue;
> > > +
> > > +				if (!lcore_config[idx].detected) {
> > > +					RTE_LOG(ERR, EAL,
> > > +						"lcore %u unavailable\n", idx);
> > > +					return -1;
> > > +				}
> > > +				lcore_config[idx].core_role = ROLE_SERVICE;
> > 
> > Why not to use rte_service_lcore_add(idx) here. So that in future some
> > changes we don't need to touch this file.
> 
> The issue here is that the hugepages memory that service-cores requires is not available at this point. Keep in mind, the EAL parse-opts runs before almost anything else (makes sense, given we can specify e.g. --no-huge).
> 
> Given that there is not rte_malloc() available at this point, we have a few options:
> 1) Use existing allocated mem, e.g. the lcore_config[] array as above.
> 2) Delay the parsing of service-core mask until later. Breaks "parse -> validate-> config -> run" workflow.
> 3) Allocate temp memory to store the service-core indexes, and later free that back (feels hacky to me?)
> 
> Current scheme of (1) makes the most sense to me.

Yes. Make sense to keep option 1.

One suggestion:
There is a lot duplicate code between new eal_parse_service_coremask() and
eal_parse_coremask() on the same file. I think, we can add a common parsing logic
and on match, the actions can be invoked through function pointer which
is passed in the parsing function.

> 
> 
> > I added following code in unit testcase and I have 8 cores system. So I
> > was expecting cores prints from "0 3 4 5 6 7" as lcore 1 and 2 will be
> > stolen by service core. But it looks like RTE_LCORE_FOREACH not honoring
> > previous rte_service_lcore_add() functions.
> > 
> > testsuite_setup(void)
> > {
> > +       int i;
> > +       rte_service_lcore_add(1);
> > +       rte_service_lcore_add(2);
> > +
> > +       RTE_LCORE_FOREACH(i)
> > +               printf("cores %d\n", i);
> 
> 
> Root cause found - and fixed. If you don't strongly object to lcore_config[] method above, then I can prioritize this and try get a patchset up ASAP.

Great!!

>