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Date: Mon, 13 Oct 2014 23:04:32 +0200 From: Richard Weinberger <richard@....at> To: dedekind1@...il.com CC: linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 3/4] UBI: Fastmap: Care about the protection queue Am 13.10.2014 um 17:23 schrieb Artem Bityutskiy: > Well, used and free are RB-trees, looking them up is slow. This is true but we'd have to look it up in multiple trees and the protection queue... > If what you need is to go through all used and free PEBs, then you can > introduce some kind of > > struct ubi_wl_entry *ubi_wl_get_next_used(struct ubi_wl_entry *prev) > > function, and similar functions for the free. > > I would return you the next entry (or NULL would indicate the end), and > it would take the previous entry as the input, or NULL for the first > call. > > We'd need to take the locks before calling this function. This is > cleaner than what we do now, right? ubi_update_fastmap() takes ubi->wl_lock anyway to block any changes in the free, used, etc. trees to make sure that the to be taken state snapshot is consistent. >> But we could add the state information to struct ubi_wl_entry by adding a single integer attribute called "state" or "flags". > > But there is a price - memory consumption. We do not want to pay it just > for making the inter-subsystems boundaries better, there ought to be a > better reason. > > Say, for an (imaginary) 8GiB NAND chip with 128KiB PEB size this would > cost 256KiB of RAM. Is 128KiB PEB size still realistic on modern NANDs? Even if, 256KiB are not much and the kernel consumes this additionally with every new release. But I can understand your concerns. > Squeezing the state into the last 2 bits a memory reference would be > another possibility, BTW. Not elegant, though... > >> Would this make you happy? :) > > Not very, I'd save this for the last resort solution. Okay, I'll try harder to make you happy. Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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