From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailserv2.iuinc.com (qmailr@mailserv2.iuinc.com [206.245.164.55]) by sod.res.cmu.edu (8.8.7/8.8.7) with SMTP id PAA27555 for ; Thu, 25 Mar 1999 15:31:48 -0500 Received: from psalpha2.cup.hp.com (psalpha2.cup.hp.com [15.13.189.229]) by atlrel1.hp.com (8.8.6 (PHNE_14041)/8.8.5tis) with ESMTP id PAA19106 for ; Thu, 25 Mar 1999 15:31:28 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by psalpha2.cup.hp.com (8.8.6 (PHNE_16852)/8.8.6) with SMTP id MAA27090 for ; Thu, 25 Mar 1999 12:31:37 -0800 (PST) Message-Id: <199903252031.MAA27090@psalpha2.cup.hp.com> To: hppa-linux@thepuffingroup.com Subject: Re: [hppa-linux] Qn on PA-RISC Page tables and TLB In-reply-to: Your message of "Wed, 24 Mar 1999 23:10:36 PST." Date: Thu, 25 Mar 1999 12:31:37 -0800 From: Craig Hada List-ID: > > > PA-RISC Arch 1.1 book says: > On page 3-14: > > Exact form of these tables is s/w convention. > > Q. If the format is software convention, does that mean > the fields within TLB slots are not defined by Hardware ? > Though the book does seem to indicate what fields are needed > in a pdir entry. Without knowing exact positions of various > fields how would TLB entries be updated from pdir entries in > memory ? > In the absense of a harware TLB walker, the page directory format can be structured by software to fit its needs. However, the TLB miss handler must reformat the bits to fit the format of the TLB insert instructions. To get maximum performace from the system, the TLB miss handlers must be made very efficient. The format of the page directory entry in the PA-RISC Arch 1.1 book minimizes the work of the TLB miss handlers by aligning the fields to match the format of the TLB insert instructions. In order to enable the hardware TLB walker, the format of the page directory must match the format from PA-RISC Arch 1.1 book. In addition, the memory for the page directory must be equivalently mapped, power of two size aligned (ie a page directory 1 MB in size must start on a 1 MB boundary), and contiguous. > Other interesting point to note is that PA-RISC does not > define how many entries in the table etc. Very much unlike > x86. > > -pkd The number of entries in the page directory are a function of the amount of memory and the amount of memory mapped I/O in the box. Since the hash function is not perfect, the size of page directory can be tuned to meet the system requirements. -Craig > > > > > > ------------------------------------------------------------------------- > To unsubscribe: send e-mail to hppa-linux-request@thepuffingroup.com with > `unsubscribe' as the subject.